craigslist won't be disrupted for the simple reason because they have a ton of traffic...UI etc, is pointless for classifieds since the only thing people care about is whether or not the service has buyers/sellers for the things they want...and Craigslist has that in spades.

i.e. I recently listed a car for sale on craigslist...listed it on Friday evening and got 8 interested people in a few hours, and it sold the next day.