Facebook/Google comparisons always strike me as way off base. It's like comparing a Central Park (busy, no money) with Disneyland (busy, big money).
Why? Popularity as a free service doesn't necessarily imply that said popularity will be retained upon introduction of a monetary fee.
Like it or not, facebook has real utility (just like central park), and people are willing to pay for real utility in one way or another.
A lot of people don't think Facebook is a business either.