It's not just about how good the site is, or what features they have. There are huge network effects. If you're a buyer, you want to go where there are a lot

It's not just about how good the site is, or what features they have. There are huge network effects. If you're a buyer, you want to go where there are a lot of sellers. And vice versa. And Craigslist has that. If anyone wants to become a serious threat to craigslist, there is a huge chicken-and-egg problem to overcome.