Where have the rest gone?

Boddunan is aiming to achieve 10,000 registered members ...perhaps this number may be achieved this month itself. It's really a big thing. But the problem is how many of those registered 10,000 members are making use of this site? I think number of participants are below 25. Am I not right? :(
What happened to other people? How can we bring those people back to our site? I think it is more important to see even 100 people actively participating in forums and writing articles rather than seeing 10,000 registered members on the home page, who are not actually using this site.
What is your opinion and what are your suggestions to bring those registered members back?? :)