Yes the calls are free. But you're paying for the mobile access and that drives usage and something that drives usage is good for the operators.
Until now, we've been primarily focused on PCs. But our customers want a more ubiquitous experience. And, with a service for mobile phones, we plan to deliver this.
At no charge, if they both have the software installed. Or by using SkypeOut if they need to call a land line or mobile at low rates.
At the office, we actually don't have a land phone line. We use Skype mostly, and mobile phones to receive calls from people not on Skype.