Isn't it in-app advertising? If so then it's even worse. My understanding is that cookies are not shared across apps, so the advertiser on app1 cannot correlate your identity with the one on app2, defeating cross-app tracking (the app equivalent of cross-website tracking). If you make it a central, Appled owned (i.e. access to much more information) then you re-enable cross-apps tracking.
However since at least 3 majors versions of iOS, iAd have an opt-out switch to allegedly prevent any tracking. I even think this opt-ou switch is now an explicit part of the set-up procedure when you activate the phone.
You still have to trust Apple that this opt-out is effective. But I really see more harm than good for them should they actually be lying about that.
