After WPP reckoning: The case for and against principal media

Look no further than the recent WPP whistleblower filings that’s dominated headlines. In the filings, a former WPP exec critiqued GroupM’s trading practices, including its rebate-driven deals.

Whether it’s billed as principal media, principal buying, principal trading, rebates or kickbacks: a rose by any other name. There’s nuance, but they all refer to the same practice: agencies invest in media at non-disclosed prices to then resell to their clients, presumably at a markup to the agency.

While not new, the WPP debacle has kicked up dust and forced advertisers to rein in their agency partners over hidden media practices. Don’t call it a call for principal media prohibition. Rather, it’s a demand for clarity and standards as agencies grapple with shifting compensation structures.

“Yes, the agency is offering you good value, but you’ve got no real straightforward way to know whether or not that’s the best value available, because the entity helping you arrive at that decision is also profiting from it,” Seb Joseph, Digiday’s executive editor of news, said on a recent episode of the Digiday Podcast.

On this episode of the show, Joseph and Michael Bürgi, senior editor of media buying and planning, discuss the pros, cons and nuance of principal media buying.

This interview has been lightly edited for clarity.

The case for principal media buying

Bürgi: As we know from WPP’s 2025 financial results, it is not a holding company that is in great shape right now. It’s in the midst of massive transformation. They’re trying to simplify the offering, but along the way they would argue they need to make money. Principal media is a way to make money because of the markup that they can charge their clients for that inventory that they have purchased, for what is probably a much lesser price — as long as, and this goes back to the Forrester report and what I constantly hear from consultants, there is some transparency about what they are doing.

The case against principal media buying

Bürgi: If an agency is buying crap media for really cheap and then marking that up to the client — and the client is having its ads put in there, and they’re not getting the return on that investment — there’s going to be a problem.

Joseph: The difference really comes down to the fact that the agency is buying that media inventory for itself first, and then it re-sells it to clients. It’s almost inverting that brokerage model. In that paradigm where you’ve got the agency simultaneously acting as an advisor and your supplier, that’s where things as you were saying, start to get a bit [underhanded].