Robert,

Easy to start, hard to maintain. The main problem I see is sellers remembering to remove listings for chips they have sold or traded away. One time sellers would add chips to the listing, sell them all then ignore the need to remove the listings. It wouldn't be long before the database was clogged with items that weren't really for sale anymore.

Another problem, users forgetting their passwords and not being able to change their own listing. That would turn it into a headache for the database administrator.

I don't mean to be negative about your idea, it's just that I've tried to think this one through a few times in the past.

Greg