[Mgccl]

Why do you want to make a new social network?

If you goal is to make money, then ignore this comment.

If your goal is to make something better than facebook, you want to ask yourself, why you want to reinvent the wheel? Unless you have some great idea. Don't.

Check out Diaspora, maybe it's better for you to work on that when it comes out. They have some good ideas. You can also look around other open source SNS.