That number, however, could be as high as $4 billion by 2009, depending on the average price per call and actual market penetration, which could range between 5 percent and 15 percent, The Kelsey Group said.
Pay-per-call, which is offered by some of the major web portals, makes particular sense when dealing with local products and services.
"Consumers are accustomed to making phone calls to contact local businesses and local businesses are similarly used to closing leads over the phone," Kelsey analyst Greg Sterling, said in a statement. "A performance-based online medium that delivers calls rather than clicks therefore makes sense for the local market."