There is a reason why Google Talk came out. What do you get when you combine Google VOIP + Google Ads + Google Print Ads = Google Pay-Per-Call advertising model. Google won’t be the first ones who are using this pay-per-call format.
With Google Talk I can imagine an ad that’s on the IM screen which changes depending on the IM conversation. And once the person clicks on the ad it is auto connected to the company’s customer service center. Once the person is connected to the center they will be able to order whatever the ad was for. Very cool and very profitable. Google will be able to charge a higher amount for this type of ad given how targeted it is.