*sigh* I just lost a big post so I'm going to have to summarize.
Facebook is awesome. With the new Facebook applications initiative they've established themselves as the premier social network. For startups looking to create a new kind of social network site around a particular niche, they don't have to start from scratch. They can leverage Facebook's community and technology and just build a layer on top. This is mutually beneficial since now Facebook gets all these cool features without lifting a finger.
Of course there arises the issue of TOO MUCH like what has happened with MySpace, but with Facebook's cleaner design and limitations on modifying the CSS of the profile, things shouldn't be as ugly. Facebook has a brighter future in the long term than a closed space like MySpace. I think MySpace is going to go the way of the AOL.