And clear social recognition is a natural measure.
Can't that be abused too? Why not just tell a bunch of people to link to your site under a false pretense of say some kind of reward? Like the old tricky approach of "pass this email on (link to this site) to 20 friends and Bill Gates will pay you $$$$". Or how about actual paid links from social site users? I can hear the gears spinning already on "how can we beat this"? Word of mouth is great until it becomes PAID word of mouth, and how can Godzilla determine that?