With the recent announcement from google about opening up re-targeting through adwords and plenty of venture money flowing into re-targeting companies, there is little doubt that ad re-targeting works.

“The conversion rate is similar to paid search,” he says of Criteo’s retargeted display ads. Retargeted ads are typically clicked on four times more than a traditional run-of-site banner ad, he estimates.

This is all well and good, but when I going to be able to re-target the visitors to my competition?

e.g If I am Target.com, I can re-target visitors across the web who have visited BestBuy.com and offer them a competing offer on a product they have viewed at BestBuy.com or a coupon for $$ off their order.

Best Buy will not be pleased that the data they are sharing to power their own re-targeting campaign is being used against them, but the end user benefits with a better price, and net sales are increased as a result, creating a win for both the merchant (who makes the sale, the user and the advertising network).