The Federal Trade Commission is investigating Apple and Google for collusion, because they share two board members (Eric Schmidt and Arthur Levinson).
Sharing board members becomes a problem under antitrust law when the two companies are competitors and they are coordinating their strategies. Apple and Google are primarily competing in mobile phones. As I understand it, though, Schmidt recuses himself when Apple’s Board of Directors discusses the iPhone.
We’ll see if this goes anywhere, but I doubt anything will come of it.