Facebook's effectiveness for retailers hunting baby boomers poses a major dilemma – and not just to retailers. Brands are at the mercy of walled garden keepers – who have built higher walls since GDPR regulations kicked in. All marketers are grappling with the same paradox, as are publishers. They need Facebook's unparalleled reach, yet the more data and process they hand over, the greater their exposure to risk, and the more powerful the platforms become. Unwinding the marketing plans that created this vicious circle is no mean feat, even for those with the stomach to wrest back control. But that's part of what Publicis hopes to convince brands it can deliver with its acquisition of Epsilon – if it can scale the U.S. focused customer experience management platform globally.

Implicit in the statement that Facebook works particularly well for the middle aged and elderly is its reduced efficacy for younger shoppers. As Facebook skews older, that poses an audience challenge for marketers – and an opportunity for channels that can better drive the under 55s into digital and physical stores.