Privacy problems arise in advertising because companies record our searches, page visits, purchases online, purchases offline, and other behavior to try to predict what and when we will buy.
Paybuyer's verification-based advertising system eliminates the need to keep detailed records of our activity because it doesn't predict. It asks each user what she plans to buy, delivers ads based on what she says, and then verifies whether she actually buys.
And, because the system verifies probabilistically - by random sampling - it checks only a tiny fraction of purchases.
To deter double-dipping and free-riding cheats, Paybuyer keeps a very small amount of data on how users use Paybuyer itself, but these data are erased (except when cheating is detected).