I actually spoke with them about a year ago. At that time I believe it was a $10,000 minimum to advertise with them. They can very specifically target the audience you want. But you pay them per impression and I was scared to invest that much money just to try it out.
Didn't know how good the traffic would be. I was gonna run a zip code campaign and if it did profit for me there was a chance that it would not have converted well for the merchant and they might not have payed me. So I choose not to do it.