A year since it's introduction even Google is surprised by how successful "Click to Call" has become. "We're seeing millions of calls every month; it has become a core part of a large number mobile search ad campaigns," said Google's Surojit Chatterjee who is in charge of the product.
Google Product SVP Jonathan Rosenberg on the company's most recent earnings call also mentioned:
[The] Click-to-Call ads are generating millions of calls every month. A lot of advertisers are running these campaigns. I think one you can see if you tried is DirectTV. We did launch a call-only option where the only clickable link in the ad is actually a phone number, which not surprisingly substantially increases the click through rates on mobile devices.
And we've extended some of the desktop formats pretty successfully to Mobile. Sitelinks is one. If you try a query on Oakley, you'll see one, if you seller ratings on something like running shoes . . . At the moment, I don't have any specific comments on NFC other than to go back to the statements that I've made in previous calls, which is when people are completing transactions with these devices, it becomes much more trackable and obviously significantly more valuable.