WOW! Here is the post by Marc Andreessen. They are seeing a 1000 social networks being created per day. Earlier today, I read on Demo.com that there are 70+ products competing in the space. That is a lot of social networks.
The demo article also talked about several products that build social networks around events:
Small World Labs, introNetworks, CrowdVine, Leverage Software, and EventVue are among the ...I browsed some of the sites. Hope to use one of these products to build an on-line collaboration site for the CTO Roundtable.