> Not sure if reputation mechanisms would work in a site where people often post just once, and that doesn't require creating a user account in order to post.

That's a weird premise to me. If you post an apartment, you could just as easily also want to find a girlfriend or buy a used bike or avail yourself of any of craigslist's other categories. That's their big value, after all – everything under one roof.

The fact that craigslist doesn't require a user account to post is an extremely dubious product decision at this stage.