I think having a 'give us your email address' as the first step may be turning people away. If you allowed authentication through twitter, facebook or linkedin, people may be more inclined to participate.
Ooh - that is a great thought. I was wondering if that could be a part of it. Anything else?
I rolled up to the site and my thought process was 'theres not enough information here as to what this site does, so im not prepared to enter my email address'
That is really good insight. Ill move some of the information from my "about" page to the front.