Live cash back --- A game changer?

Microsoft Live Search cash back definitely has caught a lot of eyeballs. There are lots of discussions on the Internet, mostly, about how Microsoft is trying to buy in customers to use live search. However, look a little further behind the scene, we will see this is not just about another type of "rebate".
Google didn't invent search, they invented pay-per-click advertisement. This game changing invention has brought them billions and billions of dollars and will continue to be their cash cow for a while. While pay-per-click advertisement has significantly reduced the advertisement risk because you don't have to pay for a badly placed key work because people simply won't click them, it does not grantee that people who clicked the ad will eventually buy the product. this kind of risk can be eliminated by a new type of advertisement : pay-per-action.
Many websites have tried this idea before, some of them are actually very successful, http://rebate.com/ is an example. For most of them, the number one problem is still, search. Customers need to find their product first. So the first step of game is still search. Microsoft live search still need to improve search to get the chance to change the game. At this point, however, seems Google is still leading the game at a firm No.1 position.