I believe it's a self-hosted mashup application for all your social networks. Correct me if I'm wrong. I think it's a pretty neat idea, although most normal people are only connected to 1 or 2 social networks. I myself connect to Facebook for friends and family, and LinkedIn for professional contacts. I don't see the point of sharing personal stuff on LinkedIn too.

-update- From the looks of it, Locker only supports Facebook right now...