With pay-per-call advertising expected to boom, vendors and publishers poised to benefit from it are attempting to convince SEMs and media buyers to set aside a portion of their budgets to performance-based phone leads, writes ClickZ. Though local advertisers are expected to adopt pay-per-call advertising, some media buyers and SEMs are already giving it a shot, and pay-per-call providers are winning over distribution partners for their listings.

Ingenio, for example, has partnered with AOL, Miva, and Local.com; eStara with SuperPages.com and Amazon's A9; and Jambo with Infospace. Ingenio works with more than 30 agencies, including Performics and Carat Fusion; eStara works with Ogilvy, Digitas, and Carat, among others.

"More than half of the spending for pay-per-click advertising comes from agencies. The growth of Google and Yahoo is in part a result of their ability to reach out and work with agencies. That lesson was not lost on us," Marc Barach, Ingenio's CMO, told ClickZ.

Pay-per-call vendors are also trying to convince agencies that pay-per-call will help expand relationships with clients and bring in clients new to online advertising.