[bee_rider]

If I were Apple, I'd try serving ads something like:

Send a randomized bundle of ads to each iPhone (the ads must come from my servers). From that bundle, select the ads that fit user interests most closely. Don't report which specific ad the user was served.

This would presumably be quite annoying for advertisers, but it would preserve user privacy and, hey, Apple basically has a monopoly on users who actually pay for apps so what are they going to do? Perhaps the advertiser could be provided with some artificial profiles with statistically representative taste profiles to see how often their ads come up.