Privacy concerns trump user targeting.
This one has been coming for a while. Apple flagged up its strategy six months ago, warning developers it would act against UDID tracking because of pressure from government and sections of the media.
The UDID is an alphanumeric string, unique to each device, that's used by developers, ad networks, analytics firms and so on to track a users app and site activity. It's a pretty important tool when so many content providers rely on ad funds to monetise their business.
But Apple is worried about UDIDs because, unlike web cookies, they can’t be cleared or deleted. And there are clearly ethical concerns around tracking users when they haven't given specific consent.
According to TechCrunch Apple is already rejecting apps that record UDIDs. It quotes developers including Fluik and Playhaven as having products declined.
It says two of the 10 review teams started doing blanket rejections of apps that access UDIDs this week. Next week, that will rise to four the ten teams, and keep escalating until all 10 teams are turning down apps that are still using UDIDs.

http://www.mobile-ent.biz/news/read/...s-udids/017536