Actually, social networking sites can work really well to target and monetize traffic. For personality based sites, at least. You guys are in a different market than we are, and you are right in that the SN stuff probably wouldn't do a thing for you. But with "Amateur" sites, they are a Gold Mine when used properly. Carol spends about 30 minutes a day across all the various SN sites she plays on, and that 30 minutes brings in very targeted eyes that do sign up.
You can also think of a site like Twitter as a website newsletter, but with quick little posts that pique their attention and get them over to the site. When Carol does an update and Twitters it, we get both a traffic spike and a sign-up spike. Not bad for 15 seconds of work
But you do have to get the eyes on the account for it to work, which with Carol;'s name, is quite easy for us.