Why should an advertiser pay for a Gtalk phone call from a consumer who basically knows no more about the product than what he sees in a banner ad? On the other hand, if he goes to the webpage and is interested enough that he wants more info then the PFC option makes sense. We're doing that now at PhoneRanger viz. encouraging visitors to call us by offering them a discount. But because they're already on the page, we don't pay GOOG or Wavigo anything.