I do not think many of the enterprise wikis and collaboration suites meet these requirements. I think products that learn to mine the social space to provide intelligent resources to companies like FaceForce are more likely to come out on top.

http://blog.programmableweb.com/2007/10/15/face…

But as you say, the real issue is lack of a revenue model. Many raised this point in years past, but it never stopped investors. Invariably, the idea was that you didn't have to generate revenue. You just had to build community, since a large collective audience was worth a lot of money because of the potential advertising. If that's broken…who knows?

What's more, even in the best of circumstances, these social sites are very touchy and easily broken. Young participants are fickle. One bad incident and you're public enemy number one. I'm sure you can recall several well-known incidents in the past year.