Like dating sites, David Beisel of Masthead Venture Partners, thinks that the future of social networking sites is in verticalization:

However, I believe that there are other areas which people are passionate about which would drive them to connect. And this desire is going to drive the creation and adoption of other vertical social networks. Just like we are seeing a proliferation of vertical search sites based on the unique needs and abilities to find information with a specific data type, I think we are going to see a rise in the number of successful (and potentially venture backed?) social networks covering many subject areas where people are very passionate about a subject. I've mentioned Ted Rheingold's Dogster and Catster as an example in the past, but was only recently made aware of Leah Kramer's Boston-based Craftster.org (profitable, 50K members and growing). It looks like the recipe is: pick your passionate subject, fill in your topic here: ----ster, and stir. Long tail, anyone?

So, what company will take the Friend Finder network approach and launch social networking sites for every niche that exists?