>The main feature of my site though is a private messaging feature. This allows users to instantly message other users of their interest instead of having the inconvenience of opening another application or window for email, and as well as giving out their private e-mail account.

I don't believe that feature is good enough to make people switch from Craigslist. Messaging to me is just one click. For less savvy computer users they won't mind the extra step to email.

I admire your chutzpah though. Keep thinking of ways to make a better product than CL or ebay.