The consumer internet industry spent two decades building a huge, complex, chaotic pile of tools and systems to track and analyse what people do on the internet, sometimes for very good reasons, and sometimes with strong doses of panic and opportunism. Now that’s mostly going to change, between unilateral decisions by some big tech platforms and waves of regulation from all around the world, but we don't have any clarity on what that would mean, or even quite what we're trying to achieve, and there are lots of unresolved questions.