The Register has a short article about a new service Google is quietly testing. It puts a little telephone icon in Google ads, and if you click the icon, a little form pops up and asks for your phone number. Your phone starts to ring, and when you pick up, Google transfers the call to the advertiser.
Google promises to keep your phone number from the advertiser, but I'm always skeptical of these claims, since Google also reserves the right to change their privacy rules whenever they like. Google has your phone number, and like everything else they do, it is another important bit of information that they can use in a variety of ways to build an extensive dossier about your likes, dislikes, and buying patterns.
It is a clever system, and is probably going to rely extensively on low cost VoIP to make it work. Some businesses that require extensive customer interaction to get an order may benefit from it. But I don't think I'll be clicking on one of those little green phones anytime soon.