Google wants more action.
The search leader is developing a so-called pay-per-action ad service that could boost its coffers by billions of dollars, though some people in the online ad field say perfecting such an ad program is a big challenge.
Google GOOG gets nearly all of its revenue from pay-per-click ads placed strategically near certain search results. With pay-per-click, advertisers pay only when a consumer clicks on their ad. It's the fastest-growing segment of the multibillion-dollar online ad market.
