I think for many reasons:

• OpenID integration make easy to signup
• The interface it's clean an tidy
• You don't have to fill thousands chptcha fields
• A great tag system, easy to search
• The reputation system. It's like play on any ranked online game, it's little addictive :)
• Because the reputation system the people avoid to answer with very annoying answers like: RTFM, "Google is your friend" because they will loose points very quickly.

I love this project, it's possible to buy market shares of stackoverflow.com ? :)

I think for many reasons:

• OpenID integration makes it easy to sign up
• The interface is clean and tidy
• You don't have to fill in thousands of CAPTCHA fields
• A great tag system, easy to search
• The reputation system. It's like playing any ranked online game, it's little addictive :)
• Because of the reputation system people avoid to answer with very annoying answers like: RTFM, "Google is your friend" because they will loose points very quickly.

I love this project, it's possible to buy market shares of stackoverflow.com ? :)