you can use the N900 without a sim. But not receiving calls. you can use the N900 without a skype account. But not receiving skype call. Skype on the N900 "just works" with any user of skype, and 3G video call "just works" with any 3G user (with a video call capable device). Anyway, from what I have read some time ago, 3G call is a hard to implement, very specific telephony feature (specific codec and stuff), because it has not been designed to be used by generic purpose devices (as these use generic purpose protocols, ie voip). I'm affraid that because of this, 3G calls will never come to the N900 as: - it's not something that can be hacked or ported from desktop linux - commercial vendors -including nokia- have stopped investing in the platform. The only thing that can be done now is discussing workarounds, because basically proper 3G video calls and flash 10 will only come in PR 1.4