Have you ever heard of the network effect? Craigslist has such a lock on its market that you would have to have something extremely compelling to dislodge them. A few flashy maps and a web 2.0ish appearance wouldn't be nearly enough to do it.
Classified sites gain a regional dominance. Craigslist in canada for example, is only really dominant in vancouver, one of their biggest foreign markets. Kijiji is dominant in other towns.
