So are these qualified leads? My concern would be people fishing and wasting other people's time. Or someone that currently owns the product and is looking for ideas on how to price. Thoughts?
Like any marketplace there'll be time wasters - I don't sell on eBay anymore because of them - but in my experience, most of the time its the buyers that are time wasters.
In our case - since buyers have gone to the effort of creating a WTB listing, you could argue they're less inclined to waste sellers' time. Of course, the feedback system/reporting users would help us to identify repeat offenders and take action.
Check out our demo which should help explain things: http://www.wantobuythat.com/demo.html