When it first came out, I thought this is just like a friggin Xoops installation customized for college students (but custom built, and carefully sold to the right people). Also, a lot of Web 2.0 ideas were just like Xoops CMS modules (or WP plugins) but scaled out and adapted for mass website usage. The Facebook platform is just like Xoops module deployment that users can customize for themselves rather than the webmaster.
Theoretically, the only thing that could take out Facebook or come close, would be some type of cross-language, cross-server middleware layer, that webmasters could use that would simplify and improve web development, and give broad social, ecommerce, presence and whatever other features are, or will start to be in common. FB is in the best position to do that, and that's what I expect to see going forward: it'll have to create standards and protocols (an open source FB server?) and release those into the community.
You're not really saying anything at all, as far as I can tell.