Privacy problems in advertising arise because companies record our searches, page visits, purchases, 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, long-term records about us because it doesn't try to predict our future buying behavior. It asks each user what he plans to buy, delivers ads based on what he says, and then verifies whether he actually buys.
And, because the system verifies probabilistically - by random sampling - it checks only a tiny fraction of purchases.
Paybuyer's method requires a small amount of past behavior data to prevent cheating, but these data are erased, usually within less than a year.