CANNES, France — Retail media has spent the past few years multiplying at a pace normally associated with rabbits, streaming subscriptions and Cannes invitations. Now comes the less glamorous phase: proving that all those networks, promotions and data partnerships actually sell something. “Most of our conversations are centered around proof,” Chris Riedy , chief revenue officer of Ibotta, said during a Beet. “Every brand is happy to test something, but to keep going, you got to find the proof. ” Riedy joined Catherine Berger , vice president of marketing transformation and services at Bimbo Bakeries, and Katie Daleo , general manager of CPG ads at DoorDash.