Looks like no one can have enough of Social Networks.
In my opinion, the entire wave of networks would keep on flooding the Internet. Pertinent question would be which network would survive in the long term.
Lets not even go into reasons why these networks are created in the first place.
Things that would keep one social network ahead of another are
1. Network Effect: The network with most number of people would eventually win. People would have to join the network with most people and most people would join a network because the network has most people on it. Saw this in action with Orkut in India.
2. Repeat Visitors: Once a social network grows beyond its novelty factor, a lot of people simply stop coming back. Network should have something that attracts people back. LinkedIn: Professionals. Facebook: Applications.
If I need to talk to my friends and other random people about something, I can create a blog, I can comment on other blogs. I can send SMS, emails, call for real. The utility of a social network for daily chores is simply absent. Networks would have to offer more than just dating, friendship, music etc.
3. Offering: A network should give me something that is hard to find (or do) in real life. For example LinkedIn. This is something (access to people with IQ :D) that I cant get in real life. No popular network apart from LinkedIn offers this to me.
Apart from these three, if few networks have to emerge as winners, they need to take care of following
1. Regional networks: Even though Internet does not have any boundaries as such, currently we have different networks dominating different geographies. Friendster - Asia, mySpace - US, Orkut - India and Brazil.
Obviously the reason for this spatial distribution is real connections (you invite, join and interact with social networks where your real-life friends are and most of your real-life friends live close to you)
2. Interest Areas: End of the day you join a network and stay there because you are interested in something and you want to connect to people with similar interests and want their opinions.
Myspace could connect all musicians, Linkedin could connect all professionals etc. The social network that can do this first would end up as a winner in my opinion.
If I was to compare professional interests, FaceBook with its applications is a move in that direction but it still lacks seriousness for a QnA network and more importantly it does not have the kind of people LinkedIn has. Similarly if I was to compare music interests, Myspace and FaceBook are still not there.
In my opinion, social networks are like any other commodity. In the long run, we would have one or two major players with chunk of the market share. And the networks that can aggregate interest areas and geographic spread would emerge as winners in long term.
Social Networks - The Future
I posted an answer on Social Networks on LinkedIn.