I don't think Google can afford a $6 billion buyout. They're on track to make maybe $16 billion this year. Microsoft is probably the only software company with a decent interest in the web and the pocketbook to pay for a highly valued site. And the aQuantive buy is the biggest they've ever done (and probably will ever do).
This is (sort of) a misunderstanding of how most buyouts work. Google, were they to "acquire" facebook for $6B would almost certainly structure it as a stock-swap merger. This way the acquisition isn't a taxable event, and they can use stock instead of cash.
At GOOG's current market cap, $6B of dilution would be pretty minimal.
Not mention the $10B of cash equivalents (and growing, fast) on their balance sheet to buyback stock or even do a full cash deal if they were feeling crazy.
I suppose I was using "afford" somewhat loosely. I still think $6 billion would be a huge amount for Google to drop in one place, stock or (especially) otherwise.
