I've been playing around with a number of so-called Social Software/Social Networking sites for about six months.
I'm currently on Ryze with supposedly 13 'Friends' and 414 in 'Network', and Tribe.net with 20 'Friends' and 17,677 in my 'Network'. I've registered for a few others, but wasn't able to get them going much beyond registering. However, I have not registered for Friendster yet, as it was originally a dating site but I understand now that it is more then that.
These Social Networking sites have been interesting, but so far none have been a really useful to me.
I've identified a few problems:
Getting started can be difficult -- you have to either invite a bunch of your own friends (which can be tacky) or you have to find an acquaintance who is has already collected a number of people as their friends and join with them.
You also have to be faithful to updating your local home page, and I for one have too many home pages.
There seems to be some cache to have lots of network 'Friends', however, I'm really uncomfortable with that. There is often a 'tit-for-tat' that goes on that is "I'll add you as a friend if you'll add me". But I'd rather name them something different then a friend. In fact, a number of people that I have as 'Friends' are people that I'd rather name as 'Aquaintances', as maybe I've met them once or twice in person, typically at an event where we didn't have any in-depth interaction.
Last, but probably most important -- I'm not getting enough value from them for the effort. I do have a friend that say that she has gotten good business from it, but I think that is more because she is a single woman and because she attended some live events sponsored by the social network. Maybe my problem is that I'm a decent networker by myself, and don't need the extra help of the service?
All that I've joined feel just a bit off -- but yet I still believe there is something useful in Social Software to learn that I just have to puzzle out.