The API myth
romy.posterous.com
romy.posterous.com
By forcing everyone to use the same crappy interface, they prevent power shoppers from snapping up the best deals and diluting the quality of the postings. It's hard to find good stuff on craigslist, but it's equally hard for everyone, so the common folk have a decent shot at it, which keeps them coming back.
I love that craigslist operates this way because it's so antithetical to everything silicon valley stands for, and yet they are phenomenally successful.
I have loved and used craigslist for years, but I have little fondness for their locking out third parties. As a seller, I benefit by having more people exposed to my listings. As a buyer, I benefit from more powerful tools.