This article seems to miss a very important point: Craigslist basically operates like a nonprofit. Anyone who wants to compete with Craigslist has to have a compelling answer to the question "how do I compete with a company that does not care about profit?" in addition to the normal questions a startup has to answer.

(for the record, I think that the way Craigslist runs things is both admirable and idiosyncratic: it works very well for them, it wouldn't necessarily work well for others)