Hmm, I have a skype (and a sip) account, and contacts with a phone number are callable via skype. The contact card shows a first button for "normal" calling/texting, and then I have a section called "Services" which has two buttons, one for calling via skype and one via sip. I'm not running "1.0" but the update that you'll receive later this year, however I'm pretty sure it was also like that in 1.0. Maybe someone can confirm? Maybe also check in the setting of your skype account (on the N9, in the "Accounts" app) if there's a knob there to activate that.