Apple is tightening the reins on iOS developers who utilize IDFA, putting the kibosh on apps that use the identifier without offering up advertisements. Such activity has been against its terms for iOS developers, yet was still fairly common among many apps that are now being rejected.
News has surfaced as some developers are getting app-rejected letters from Apple, which goes on to explain the violation and encourages a code check for certain bits of code that could be causing the trouble. One such recent app to get hit was Mixpanel, which utilizes the iOS Advertising Identifier sans advertisements.
Says Apple's terms for developers:
You and Your Applications (and any third party with whom you have contracted to serve advertising) may use the Advertising Identifier, and any information obtained through the use of the Advertising Identifier, only for the purpose of serving advertising. If a user resets the Advertising Identifier, then You agree not to combine, correlate, link or otherwise associate, either directly or indirectly, the prior Advertising Identifier and any derived information with the reset Advertising Identifier.
The move could be one to tighten up privacy measures -- or, at least, keep them from being whittled at -- but why the crackdown has been initiated isn't clear. Various other bits of speculation abound, some less altruistic than others, but ultimately it boils down to a need for developers to get their apps in line with the relevant terms, otherwise a rejection could result.