OK, I may have jumped the gun in saying Facebook has "jumped the shark." Maybe it's just gone mainstream, just as broadcast TV networks did decades ago. And, in going mass, it's got a real (potential) business, but also lost some of the specialness, and become more of a platform for things like marketing and ads and so on.
As everyone's been saying all over the "mainstream" media, it's still getting hundreds of thousands to sign up every day, has something like 175 million profiles and so on. But, I'd still like to see some real figures -- how many profiles are active, how active are people 1, 3, 5, 24 months after signing up (growth or diminished)? for how many people is it a regular habit? Is Facebook Connect -- which allows folks to do Facebook stuff outside the Facebook universe -- a boon, a help? Is there a sweet-spot demographic group? What types of users use it most? Who's really made money off it? What utility does it really serve for people? What are the revenues vs. the costs, and what's the cashflow?
Maybe the parodies (aluded to in the post linked above) are a sign of how popular it is.