The government tends to look out for and protect its biggest corporate partners, particularly those that play a strategic role (think: Boeing). The major Internet services companies are now protected government sponsored entities, just like Verizon and AT&T.
The Feds can never risk the potential that the massive orgy of data that Facebook makes possible - both domestically and globally - might unravel or be challenged by competitors that might threaten the 'total information awareness' system they've built. I would argue Facebook's well being is now considered a national security interest for the US Government, as there are few other sources that provide easy access to the lives of a billion people around the world.
I wish Facebook were merely a business.