Some of them have made a good amount of money through advertising (e.g. Imageshack). It seems like the market is probably a little saturated by now, so unless y

Some of them have made a good amount of money through advertising (e.g. Imageshack). It seems like the market is probably a little saturated by now, so unless you've got some killer feature or a base of users to market to (Imageshack started off on the Something Awful forums) it's probably not worth it.