My money's on SocialThing!
If you're like me, you don't even want to think of joining another social networking site. It takes time to create a good profile page for each site you belong to, and then there's the constant maintenance of keeping the profiles updated. And of course you want to be a member of the "right" community, which may require that you are a member of many, just to hedge your bets. (Remember Friendster?)
I began thinking that there must be an opportunity to break down the walls between all these Social Networking sites. Can I just be one person who interacts with multiple groups of friends? Well, now there are two options that claim to let you do that. SocialThing! and FriendFeed. There is a very good snapshot on TechCrunch , which compares the two services quite well. ReadWriteWeb also has a good interview with the CEO of SocialThing!
As I see it, the main difference between the two is that Socialthing! allows you to multitask. It simplifies the job of updating Social Networking sites because it will post your updates to all the profiles you maintain. FriendFeed basically aggregates what you are doing on all the other sites, and posts that activity on FriendFeed. So, FriendFeed doesn't ease the pain of updating all the sites. It just allows my friends to monitor my activity on all of them.
Earlier I talked about how good Social Networking allows people to do things online that they would already want to do. From what I can tell at this point, Socialthing! does that very well. It allows me to communicate with all of my friends more easily. Information flows from me to others. I can use it how I want. FriendFeed allows my friends to watch what I am doing with all my other friends. Information about me is exposed to others. Historically people tend to shy away from that, even if they like the novelty at first.
So my prediction is, if people value simplicity, then Socialthing! will win.