I have complex feelings about this. As a libertarian type I say one forces you to use Google (yes, I know they're by far the most effective ad network). I don't feel like their natural monopoly in search has hurt me much. Normally I would not see any reason for the US to get involved in GOOG's business. On the other hand, I have seen Google do its very best to pervert the free market. Their name appears well over 300…
I really wish there was more understanding that economic theory is essentially political, that markets are about political power relationships, not about goods and services, and that there's always a government of some kind as a central enforcer behind every market - and it probably isn't truly democratically accountable, no matter how often people get to vote.
Monopolies and cartels that treat customers with arrogance and contempt are the inevitable, predictable products of competitive market capitalism.
And antitrust is a political weapon, not a moral or economic one. Google will not be hit with antitrust action unless it makes some political missteps. I expect that for now, it's far more useful to keep Google intact.