The US government is reportedly now investigating Apple for the terms in the iOS 4 GM license that restrict rival ad networks owned by competing platforms -- i.e. Google's AdMob. Independent ad networks are not effected, nor is Apple's own iAd platform.
According to two people close to the situation, US regulators have already taken an interest in Apple’s actions, though it is not yet clear whether it will be left to the Federal Trade Commission, which carried out the recent Google investigation, or the Department of Justice to take an investigation forward.
This follows other reported probes into Apple's restriction on cross-compilers -- i.e. Adobe's Flash CS5 packager for iPhone, and its position in music -- i.e. Apple's decision to not promote tracks that gave rival Amazon MP3 a 24hr exclusive.
Google's AdMob acquisition itself faced intense US government scrutiny due to its dominant position in the online advertising market. Both Apple and Google want to buy AdMob, with Google winning out and Apple purchasing Quatro Wireless to power their new iOS iAd platform instead.
If one thing is clear, it looks like PC-underdog Apple is a high profile investigative target in the mobile space.