There's a limit to how many campaigns you can be a part of as well since one could display an arbitrary set of campaigns to you and understand who they targeted once again. In any case "show this guy an ad" like you quote, won't leave signs or campaign IDs in the apple framework unless there's a way to track that user explicitly. And tagging people that viewed ads is not anywhere in the scheme for apple. As an aside, attribution of online ads is vastly more sophisticated than you paint it and it involve statistical and causal models. https://dl.acm.org/doi/abs/10.1145/2020408.2020453 https://pdfs.semanticscholar.org/eaa4/875ae2376d681e156dcc3b... https://research.netflix.com/business-area/marketing-and-gro...