Social networks are valuable two big reasons:

1. They cheaply attract eyeballs to your pages
2. They provide heaps of data about your audience

For reasons to be addressed in a later post (or in my recent FOWA presentation, if you were one of the five people in the audience), both of those benefits are best achieved via targeted, niche communities. That means YOUR community, not those big social networking warehouses. Until recently, setting up a scalable social network with plenty of rich media, Widgets, and whatever else was a big pain in the ass.