I'm having a hard time understanding the demographics that Wantsy will be catering to. There is an obviously visible market, but I just don't understand it. Several million listings per year -- it's a modest number, but still enough for a niche market.
BUT - what compels people to post a wanted ad rather than dig through the For Sale listings to find what they want? I see wanted ads for things like "GameCube" or "New notebook" or "Red Corvette". Why a wanted ad? Is it easier to simply post what you want, and then let the sellers come to you with their offering?
I think by applying more advanced (but not necessarily more complex) features, we might be able to increase the potential market size. I'm really interested in the tagging and RSS aspect of Wantsy. I'd like to think that this might be the first marketplace that really relies on RSS and notification; I'd like to get to the point where a user can simply select tags describing what they want, instantly notifying sellers.