It's simple.
Probably the only sustainable competitive advantage in marketing is: distribution.
What Google bought was Youtube's distribution........its share of the market called video sharing.
And while pundits are arguing back and forth about how to monetize this market, and how valuable this market is in dollar terms, there's no doubting its value in the incredibly precious currency called 'attention'.
Attention is what advertisers crave, and social networking can deliver it to them in spades.
The only questions are: 'how', 'how much' and 'when'.
No?