The Financial Times is reporting that US anti-trust regulators (which could mean the Federal Trade Commission and/or Department of Justice) are looking into allegations that Apple's mobile-advertising network iAd is a potential monopoly.
The major bone of contention are the terms and conditions that allow iAd to shut out advertising from rivals, such as the Google-owned "click-vert" network AdMob. Ironically, Google's recent purchase AdMob came about BECAUSE of Apple's own purchase, earlier this year, of ad network Quattro (which is at the heart of iAd); the Googsters were able to say "Hey, WE'RE not a monopoly — our crosstown rivals in Cupertino have an ad network of their own!"
Apple is already being investigated for anti-competitive practices related to their marketing of digital music through iTunes, as well as their blocking of Adobe Flash from iDevices. But like those, the iAd investigation (which is still in its VERY early stages) must prove that Apple's policy is actually harmful to consumers — not just rival suppliers — in order to build an anti-trust case.