updated 08:56 pm EDT, Thu March 21, 2013
Also requires that all new Retina apps must support iPhone 5 display
Beginning May 1, Apple will automatically reject any app updates or new applications that access Universal Device Identifiers, or UDIDs. Apple deprecated the method of tracking user statistics with iOS 5 and has been previously rejecting apps that read the UDID without user permission for at least a year, but the new deadline is seen as a hard limit that will require developers and advertisers to use other measures, such as the Vendor Identifier or Advertising Identifier introduced in iOS 6. Most apps have already changed over.
The UDID was most often used by advertisers to track the performance and effectiveness of advertising, and was useful in developing pricing models for paying app publishers a commission based on the response rate of in-app ads. A large number of "free" apps in the App Store and in other mobile eco-systems rely on in-app advertising to sustain the application's business model. Apple had previously banned an alternate method of bypassing the UDID restriction known as "cookie tracking."
The company also alerted developers that starting on the same day, all new apps and app updates must be built for devices with Retina displays, and that all iPhone apps must also support the four-inch display of the iPhone 5. This is the first time Apple has set a deadline for Retina support, and comes on the heels of a note to podcasters asking them to increase the size of standard cover art from 300x300 to 1400x1400.
The change away from UDIDs has prompted predictable complaints from advertisers, but Apple provided at least one alternative method for tracking in response -- the Advertising Identifier. While users can opt to turn the tracking off, it is on by default.
Turning the control off does not lessen the number of ads, but prevents advertisers from gathering user data that would be used to target ads more aimed at the users' interests based on what they responded to or sites they frequent. Developers and advertisers are also free to create other methods of measuring ad effectiveness or gathering granular usage data on apps, and developers can opt to share granular data on app usage they collect through Apple's Vendor Identifier method.
Due to a number of well-publicized abuses of user data being collected without explicit knowledge or permission, Apple has tightened controls on what user data can be accessed by apps, and now requires explicit permission even if the information access requested should be obvious (for example, a photo-editing app asking for permission to access a user's photos). Users and lawmakers have made it clear that they view unauthorized reading of UDID data as a breach of privacy, since although the UDID is "anonymous" and only tied to a device, the device generally belongs to a single person -- and consequently makes it easy to associate the data to an individual.
Users are generally unaware of how much information is gathered about them through their use of "free" sites and applications that rely on advertising. Google's entire business model, for example, relies on being able to target advertising by correlating ads with user interests. Despite the many services and programs the search giant offers, 96 percent of its revenue comes from advertising sales, meaning that all of its offerings are basically vehicles for furthering ad sales.