[TravisLS]

Fair point. If you prohibit everyone, including walled gardens, from targeting based on user behavior or user data, that seems like a plausible solution.

It's a purely regulatory solution, though, not technical as the top level comment suggested :)

[ece]

Opt-in user targeting could still be fine (like offline loyalty programs), and it would be healthier than the current norm of opt-out through ad-blockers.