Retail media crossed $140B globally this year, and for most of its short life it has operated on a simple arrangement: the retailer sells you the ad, hosts the transaction, and grades the result. ROAS numbers that would be laughed out of a Meta review pass unchallenged because the walled garden is also the cash register.
The cracks
Three of the five largest CPG advertisers we spoke with now run independent geo-holdout testing across their retail media commitments. Early results are brutal for the mid-tier: several networks showed incrementality below 15% — meaning 85 cents of every "attributed" dollar would have converted anyway. The top networks, to their credit, held up: strong incrementality on new-to-brand segments, especially in categories with real discovery behavior.
What changes
Budgets won't leave retail media — shelf position is leverage, and joint business plans make spend sticky. But the internal narrative is shifting from "retail media is efficient" to "retail media is a trade cost, some of which happens to be media." Expect 2027 planning cycles to split those line items — and expect the networks that survive the split to be the ones that opened up to third-party measurement first.