After some concern over the market, I think it's time to change gears.
After doing some research, the general census of the initial wanted-ads market doesn't appear to be all that good. The response I get most often is "...why would I list a wanted-ad on your site when I can just find what I need on eBay?"
That's a good question, and I don't have a good answer. The problem with wanted-ads is that, while it's awesome for sellers, it simply won't attract buyers because they'll be too busy using other channels to satisfy their want(s). We need to apply the Wantsy concept to a market that doesn't have a lot of channels for the buyers, and a market that is really buyer-driven.
What is that market? Advertising. While everyone is being blinded by text ads, the remaining 75% of the market is left untouched. Sure you have services like AdBrite, but are they catering to off-web media? Are they really catering to the buyers? As an ad distributor, I can honestly say it'd be much easier to sell my inventory if I can see the buyers. As an advertiser, I can also honestly say that listing my need and having it fulfilled by an ad distributor who can flex is about the best option that currently exists. Having ad distributors upload all of their inventory in hopes that they'll get a buyer is too time consuming. Advertising is really a buyer-driven model, and I think it's a nice niche.
Tony Wright and Steve Poland really opened my eyes to that market (Steve pushed me to do more research), as well as Fred Wilson, who noted that the wanted-ads market was serviced by Craigslist (although, I think he missed the fact that it wasn't just about wanted-ads).