As I've written before, social networking sites are worthless if they don't succeed in building communities, so I was struck by this report by Christine Herron on the story of Flickr, as told by co-founder Caterina Fake at the recent BlogHer conference:
The Flickr team spent a lot of time greeting every user that came to the site, offering them help on how to get engaged with the rest of the community. Through this, they discovered that online community-building is just like being the host of the party - if guests come to a party, and they don't know anyone, and no one shows up to take their coats and introduce them around, they'll leave. These social networking skills are essential practices to bake into community management. Eventually, you'll want people to identify enough with the community that they themselves will act as the community police, kicking out trolls and making new users feel welcome. This community will also provide much of the user education in a socially networked site - people tend to come once invited there by a friend for a specific purpose, so they come with some idea of what they will be able to do and how the site works.