Compete, the website-measurement startup, announced that Microsoft had boosted its share of U.S. search queries by two-thirds from May to June. Microsoft's share is still small: It grew from 8.4 percent to 13.2 percent of the total market, largely at Google's expense. So how did it do it? The answer is simple: payola. Microsoft's Live Search Club offers prizes to search users. But other search engines have offered similar payoffs to spur traffic with far less dramatic results. Here's why Live Search Club is succeeding as a payola scheme — but failing as a business maneuver.