Apple sets a May 1st cutoff for new apps that use UDIDs
 

Apple has been weaning app developers away from UDID and its privacy concerns for more than a year, but it looks like the company's about to put its foot down -- and up the hardware support requirements in the process. As of May 1st, the company will stop accepting new app submissions that demand a UDID to single out individual devices; creators will have to use the ad and vendor identifiers that came with iOS 6. They'll also have to develop apps for Retina displays as a matter of course, including the taller iPhone 5 screen. We can't imagine that the news will please those who have a need for legacy UDID support, or can't easily update a long-serving app for Retina screens, but Apple clearly feels it's time to move on.

http://www.engadget.com/2013/03/21/a...that-use-udid/