Ad Tech Briefing: As AI promises ‘transparency,’ more light is shed on the ad tech tax

For the idealists out there, it’s the fulfillment of Adam Smith’s centuries-old vision of the “invisible hand” of the market, although, amid the shock of the new, there’s an even older adage: “money talks.”  

It’s likely that your social media feed reads like that of the typical Digiday-staffer, with musings on the importance of agentic technology standards, such as “Should I back Ad Context Protocol or some other standard?” 

However, in court documents filed as part of a whistleblower case pitting the ad agency holding group WPP against a former executive, there’s a reminder of how ad budgets really get directed. 

Among the exhibits, which first emerged late last week, is a report from the plaintiff addressed to their WPP higher-ups, suggesting that most supply-path optimization efforts are for show. 

Per the plaintiff’s case, WPP, neé GroupM, operated a hidden profit center by systematically retaining rebates that should have been returned to advertisers. 

The tactics through which these discounts are achieved will hardly be news to Digiday readers, with tricks of the trade such as aggregating spend to trigger volume-spend discounts, i.e., “rebates,” all part of the great supply-path optimization efforts of the late 2010s. 

However, according to the latest legal filings, GroupM would allegedly reclassify all concerned inventory as “proprietary media,” then sell it back to clients through opt-in agreements, and book the spread as “non-product related income.”  

Per the plaintiff, a former high-ranking WPP executive, Richard Foster, WPP’s trading arm would generate billions per year and retain somewhere in the region of half of those fees without disclosing this to clients. 

A more detailed account of the proceedings is available here, but it’s worth noting that the latest filings show where the lion’s share of the budget is directed. Globally, Google accounted for $9.4 billion in spend, Meta $3.7 billion, TikTok $1.1 billion, Amazon $1.1 billion and The Trade Desk $1.1 billion. 

It’s important to note that WPP denies the allegations and is defending its practices in court, having moved to dismiss the case, arguing that the plaintiff’s motions amount to a shakedown.  

However, if the court rules in favor of the plaintiff, it surely demonstrates how the ad tech tax continues (much like the cockroach), and should have tongues wagging at next month’s ANA Media Conference.  

Then again, maybe that’s an idealist’s POV, with the in-house movement likely to remain a minority?

Numbers to know

Key updates from the latest earnings season round:

• $17.3 billion: Omnicom’s 2025 revenue.
• $6.4 billion: Walmart’s 2025 advertising revenue.
• $68 billion: Amazon’s 2025 advertising revenue.

What we’ve covered

As it ramps up push to fund AI bets, Meta makes a new play for agencies

The social media behemoth has built a new team dedicated to serving teams at independent media agencies, a notable development as the industry’s ‘big six’ start to take on a different hue. 

Why Amazon believes its premium streaming inventory is worth the money

Digiday obtained an Amazon pitch deck outlining why the e-commerce giant believes its platform offers a better experience than the average 36% ad tech tax on other platforms. 

What we’ve heard

“How does a publisher or SSP automate direct sales with agents?”

– Bedrock’s engineering lead, Damian Naglak, breaks down how the IAB Tech Lab’s recently unveiled seller agent operates under the hood. 

What we’re reading

Dentsu and WPP quietly exited The Trade Desk’s OpenPath

Adweek’s Trishla Ostwal confirms that two of the industry’s largest agency holding companies have paused the demand-side platform’s “direct-to-publisher” model, citing concerns over decisioning transparency and hidden fees. 

NBCUniversal is suing Group Black

The broadcaster has filed suit against the group, which aims to direct ad spend back to Black-owned media outlets, alleging breach of contract and seeking nearly $36 million in unpaid invoices. 

Walmart’s ad revenue totaled $6.4 billion in 2025 

AdExchanger notes that the U.S.’ largest retailer (IRL) is beginning to see its e-commerce flywheel spin.

Bedrock platform closes seed extension round led by FirstPartyCapital, with Aperiam

Bedrock Platform, focused on delivering flexible infrastructure solutions for agencies and brands, will use the funds to accelerate product innovation and expand its U.S. go-to-market team.