It's broken because the people who go out of their way to create software for craigslist aren't largely duplicating functionality.

Want a map view so you can see all the relevant listings in one view?

Want craigslist to deliberately filter the same text or picture used for different listed apartments or jobs so you don't waste your time or get scammed?

Want to search by squarefoot or by actual bedrooms or by picture?

Apple would say "There's an app for that." Craigslist says "screw you".

It just means there's a huge opportunity to build a great craigslist competitor by building a service that has all these features.

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.

Brokenness: Show me all apartments or rooms-for-rent in mountain view with dish washers, clothes washers, and covered parking.

There's no way to (legitimately) outwardly index, categorize, or aggregate craigslist content.

(Related gripe: apartment searching in google is useless too: http://www.google.com/search?q=mountain+view+apartments It gets slightly better with searching on maps, but not by much.)

Many apartment/house finding sites have these features: search pages with dozens of checkboxes and dropdowns, and equally complex data entry pages for the people listing the apartments/houses. Yet Craigslist dominates. Simplicity wins.

Craigslist isn't a "simplicity wins" situation, it's a lockin-by-failure-of-innovation situation (see: IE6).

Their data? The data should belong to the people that produce the content Not the people that host it.

Craigslist gains value from it's users not they other way around.

How are these people a threat to Craigslist business? The more people use its data, the more valuable it becomes to post to Craigslist, and the more market share Craigslist gains. Craigslist does not lose a dime because of third-party mash-up sites.