Well, Yahoo is doing it so why not Google? Gary price reports that Google Begins Test of "Click-to-Call" Advertising Program. He shows how Google even posed a page or two on click to call; one page is at http://www.google.com/help/faq_clicktocall.html.
When you click the phone icon, you can enter your phone number. Once you click 'Connect For Free,' Google calls the number you provided. When you pick up, you hear ringing on the other end as Google connects you to the other party. Then, chat away on our dime.
We won't share your telephone number with anyone, including the advertiser. When you're connected with the advertiser, your number is blocked so the advertiser can't see it. In addition, we'll delete the number from our servers after a short period of time.
Gary also notes that Google has trademarked the phrase, "click-to-call" which is basically a pay per call service.