Help with Networking

How many total users are there worldwide on all social networks?

I'm trying to find an average number for the total number of users using social networks around the world (all social networks included).

Public Comments

1. can someone critique my paper please?! http://answers.yahoo.com/question/index;_ylt=AlVAFuhK3kqBwTdme5tEMVHExQt.;_ylv=3?qid=20080222043507AAj9oGJ
2. Don't try to make traffic to your question by answering everyone's question with your own question. People will go there eventually. There are about one billion people registered social network users.