E-Commerce Times reports on the current state of the pay-per-call market: 

Pay-per-call ads work in a similar way to pay-per-click ads, except that advertisers pay when they receive a phone call rather than a click.

Google is reportedly struggling to convince advertisers that click-to-call is a good tactic, as many businesses don't want customers bombarding their customer service centers with simple questions. The costs are simply too high.

eStara Leading the Way

Some online retailers, like Amazon.com and Verizon Superpages.com, reckon they have already proved that click-to-call can work in a text ad environment. These companies have figured out the right way to deploy the technology to make sure people can only click when they are most likely to make a purchase, or if they have a complex question the Web site can't answer.

For the most part, companies using click-to-call have not developed the technology themselves. Third party developers, like eStara, which is the leader in click-to-call deployments worldwide, have powered the trend, and their customers in this segment include Amazon and Yahoo UK.

The technology is being touted in earnings released by the companies who are using it, however. "The company introduced click-to-call, a new feature for our U.S., UK, German and French Web sites that allows customers to be connected quickly with a customer service representative who often already has the customer's account information in front of them, saving the customer time and increasing satisfaction," stated a recent Amazon.com press release.