In this episode of The Partner Marketing Podcast, hosted by Tradedoubler CEO Matthias, the spotlight turns to one of the industry's seasoned voices: Stephen Kerin, founder and director of Scale Digital. With a rich history in digital marketing, Stephen brings a wealth of knowledge and a forward-thinking perspective on how affiliate marketing has transformed into the sophisticated, results-driven domain now known as Partner Marketing.
This episode offers a rare and detailed look at the inner workings of a modern acquisition agency, the evolving expectations of Brands, the role of technology, and the rising influence of AI in shaping the industry's future.
A career built in Partner Marketing
Matthias: "Hello everybody, welcome to the Partner Marketing Podcast. In today's episode, my guest is Stephen Kerin. Stephen is the founder of Scale Digital, a full-service acquisition agency. Stephen has a wealth of experience working for, I would say, almost decades in partner marketing. Welcome, Stephen; it's great to have you here today! To start, could you please introduce yourself?"
Stephen: "Thank you. Nice to see you, Matthias. I'm Stephen Kerin. I'm a founder and co-director of Scale Digital. We're an acquisition CPA affiliate agency based in London. We're predominantly an impact agency. We work across various channels, and I think some of the things we'll talk about today and the evolution of affiliate will address the new channels that CPA affiliate activity is now enabling. We have all sorts of stuff. And as you know, all sorts of client types, as is natural in this game."
Stephen continues by recounting his career trajectory, which began in search marketing during the 1990s, before he transitioned into the affiliate space in the mid-2000s. His professional path eventually led to the founding of Scale Digital, a London-based acquisition agency specializing in CPA (cost-per-action) affiliate marketing. The agency operates internationally, working with Brands across Europe, the United States, and, more recently, China.
Stephen and Matthias share a history dating back to their time at Tradedoubler, where they witnessed firsthand the early evolution of the affiliate landscape. Stephen reflects on how that period fostered a network of professionals who have since gone on to lead some of the most innovative agencies and technology companies in the industry.
The evolution of the channel: From Affiliate to Partner Marketing
One of the key themes of the discussion is the evolution of affiliate marketing into what is now more accurately described as Partner Marketing. Stephen introduces the idea of “version three” of the affiliate channel. The first version emerged with the launch of Amazon’s affiliate program and the development of early tracking platforms like Tradedoubler. The second phase was dominated by the growth of large affiliate networks and simplistic programs focused heavily on cashback and voucher code models.
Today’s landscape - what Stephen refers to as the third version - is vastly more complex and sophisticated. Scale Digital alone has identified over twenty distinct affiliate categories, ranging from traditional content affiliates to mobile app marketers, CTV platforms, advocacy-driven influencers, and voice commerce solutions. This diversity allows for deeply customized strategies across verticals and markets.
The term “Partner Marketing” is not just a rebranding exercise. According to Stephen, it reflects the deeper collaborative and performance-based nature of modern marketing programs. Unlike traditional display advertising, where Brands carry all the risk, Partner Marketing involves shared accountability and incentive between Brands, Agencies, and Publishers. This alignment of interests makes it a true partnership model.
How Scale Digital engages with Brands
Stephen provides a detailed look into how Scale Digital approaches new client engagements. The process often begins with a referral or an introduction, rather than aggressive outbound sales. Once the conversation begins, the agency performs a comprehensive diagnostic audit, analyzing the client's current CPA activity, conversion rates, average order values, channel overlaps, and benchmarking performance against market standards.
Stephen: "We're building out sophisticated, detailed forecasts about every touch point, AOVs, ROAS, CAC, volumes, budgets, everything per market per product line. So, I think it's a mix of things and depends on whether Brands have their own resource. Some of them may have their own resource but may have a problem, so they may have a program, but they may have difficulty with a particular region, or they may have an issue with a product they're launching and need some help."
Many of the Brands Scale Digital works with initially underutilize CPA as a channel. Stephen notes that it’s not uncommon to encounter Brands for whom CPA activity accounts for less than 1% of online sales, despite its potential to deliver between 15% and 20% in a mature program.
Beyond diagnostics, Scale Digital differentiates itself by operating as a true agency - not a network or platform. It does not offer tracking solutions itself but instead integrates seamlessly with existing ones to focus on strategy, forecasting, and growth. They construct detailed projections and performance plans segmented by market, product line, and customer segment.
The agency also helps clients expand across other channels such as mobile-first campaigns, creator and influencer activations, marketplace partnerships, and connected TV (CTV) strategies.
Navigating Brand attitudes and industry challenges
Stephen highlights significant differences in vertical-specific behavior. For instance, fintech companies are often well-prepared and data-driven, with acquisition as a primary business goal from the start. These clients allocate budgets confidently and engage deeply with the CPA model. In contrast, more traditional industries like fashion or electronics may still treat affiliate marketing as an afterthought, often relying on outdated programs with minimal Publisher variety.
Another persistent challenge is that Brands sometimes misunderstand where Partner Marketing fits within their internal structure. Stephen often asks clients whether they view the channel as a marketing tool or a sales engine. He believes this is a critical distinction. Brands that classify it as marketing tend to restrict its budget artificially, while those that recognize it as a sales driver approach it with the necessary investment mindset.
Matthias: "Do your clients see Partner Marketing or performance marketing mainly as a marketing channel or rather as a sales channel?"
Stephen: "That's a really good question – it's a question that I always ask our clients: How do you see this? Is it a marketing channel or a sales channel? In fact, that's almost the most important question because I'm always interested in a budget perspective because they sometimes say we've got a hundred thousand pounds budget, and I think to myself, hang on, it's not marketing, psychologically you've got this wrong, this is a sales budget. Your only limitation should be stock. If you're a salesperson, if you're looking at it as this, it is a sales budget, and we're a sales team; it's very different to marketing teams, but again, I think this is a job for us as the agency to explain."
The misalignment of perception and strategy can hinder performance. However, Stephen is optimistic that education, performance visibility, and better attribution tools are helping shift mindsets in the right direction.
The shortening funnel and blending of Brand and performance
The podcast explores a fascinating shift in the marketing funnel. Historically, upper-funnel awareness campaigns and lower-funnel acquisition efforts were clearly separated. However, as performance creators and hybrid content strategies gain traction, the distinction is blurring.
Stephen notes that creator-driven content, performance PR, and influencer advocacy are pushing acquisition closer to the top of the funnel. This means that Brand awareness efforts can now directly contribute to measurable sales outcomes, a development he sees as healthy for both Brands and Publishers.
The industry’s understanding of what constitutes a successful Partner Marketing program is expanding. For example, Stephen discusses the increasing relevance of content-led partnerships, green and sustainable storytelling, and education-based marketing as part of the acquisition journey.
Artificial Intelligence and the future of the channel
A particularly compelling segment of the conversation focuses on the role of artificial intelligence (AI) in reshaping Partner Marketing. Both Matthias and Stephen agree that AI will fundamentally shorten the acquisition funnel even further by streamlining budget allocation and campaign execution.
Stephen discusses how Kaizan, an AI-driven platform for client services (which he has personally invested in), has improved their internal operations through sentiment analysis, automated workflows, and data-driven decision-making. While AI has yet to fully revolutionize Publisher-side media buying, Stephen believes that this transformation is imminent.
He envisions a future where Publishers use AI to create hyper-personalized content in real time, tailored to individual consumer needs and powered by data from recent browsing activity. AI-driven discovery platforms like Perplexity and ChatGPT could disrupt traditional search advertising, further changing how users find products and Brands.
Growth, market trends, and Scale Digital's 12-month outlook
Looking ahead, Stephen identifies two strategic priorities for Scale Digital. First, the agency plans to expand more deeply into the U.S. market, building on its existing client base and capitalizing on rising demand for performance-based solutions. Second, they aim to scale alternative partner channels, particularly in emerging areas such as voice commerce, CTV, Amazon programs, and advanced influencer marketing.
He emphasizes the importance of being agile in a market that is constantly evolving. Not everything can be pre-scripted; sometimes, agencies must be ready for “broken field running,” adapting quickly to new opportunities and unexpected challenges.
This episode makes one thing abundantly clear: Partner Marketing is undergoing a profound transformation. With the convergence of technology, data, and new forms of media, the channel is no longer a niche afterthought - it is a strategic growth engine.
Learn more about the new CPA marketing era and listen to the entire episode on Spotify, Apple Podcast, our website, and all other podcast platforms.
About The Partner Marketing Podcast
The podcast brings together thought leaders and professionals from across the globe. In each episode, our host, Matthias, sits down with guests to discuss the evolving world of Partner Marketing and share personal stories.
For more details, please visit www.tradedoubler.com/podcast