What would be the determining factor that would get you to switch to a new social networking site?

[Brandon]

Would it just be that all your friends are on your current SNS?
Would it be a new feature of the new SNS? If so, what would that feature be?
Would it be that the site is more of a niche community?
Etc...

Thanks for any input!

[H]

Probably the density of my real life network already on that 'SNS'. I'm a lemming!

In terms of niche communities... I find that I dip in and out of 'conversations' that take place in comments sections of online magazines I read, or bulletin boards I visit. I'd be unlikely to want to hook in to more permanent relationships with users on those sites - the connection there is a single interest or issue. On those sites, organic connections happen on an ad-hoc and inconsistent basis because users have nothing in common but that interest. (Or nothing that's immediately obvious.)

Facebook is popular, I think, because of the robustness of real life relationships - trust. New people you meet online are more likely to have more in common with you in several areas of life.

There is no user function that would make a difference. People tolerate awful usability on FB because of its social psychological dimensions.