From the NY Times, "The Gated Social Network. I don't want to belong to any club that will accept me as a member, Groucho Marx famously said. He would have loved the Web's newest social networks."
I came across an article about teams "working together when apart" that offers ideas for business social networking software. Especially the part about developing personal profiles where team members can quickly learn about each other - expertise locator, and work together. Check out the demo.