According to an item in the Wall Street Journal, the US Federal Trade Commission will take a look at Google's proposed acquisition of AdMob. It reportedly said nothing about two smaller recently announced Google acquisitions: Teracent or Gizmo5. The $750 million price tag of the AdMob deal, combined with the fact that it's one of the largest and most high profile of the mobile ad networks got the notice.

However there's almost zero chance that it will be blocked on anti-trust or other grounds. The mobile advertising space is highly competitive and there remain numerous companies that are very strong and independent, as well as strong competition for Google from Yahoo! and Microsoft. 

As I've said many times, dynamic platforms (e.g., Teracent) are the key to realizing the potential and twin goals of mobile advertising -- reach + hyper-targeting -- which would be in conflict in the absence of the ability to insert offers, locations, etc. on the fly.