I'd like to see a comparison of the competing interfaces. It's not about the functionality -- as Facebook has shown by attaining the large majority of its users after the Notes functionality was included, the ability to blog doesn't keep users away. If you present yourself as a blogging site, however, and no one wants to blog, then you're in for it.

I think it'd be interesting to see if there really was something better about the Facebook interface or if this whole thing should be blamed on network effects. People used Facebook when it was new for the same reason they use it now: the people they know also use it.