This .ning stuff is great. However, I've got a client who would like a closed (perhaps subscription-based) social network that doesn't have any advertising and is protected by a secured server.
I agree with the sentiment, Alberto. No replacement for face-to-face...However, I need something that will connect a lot of people who don't know each other across disparate geography. Judging by what I have found (which isn't much), we're probably going to have to develop some custom software.