That's true, however its not quite what I mean. We're limited to the audience that uses craigslist in that model. One idea would be to have a Twitter-like servi

That's true, however its not quite what I mean. We're limited to the audience that uses craigslist in that model. One idea would be to have a Twitter-like service where I can say "I want X" and businesses who are monitoring that service are alerted to my request.