Wouldn't skype being online all the time chew up your battery? I thought that even with backgrounder that skype wouldn't actually be connected unless the phone wasn't in "standby". But I may be wrong, haven't tested it.
Nice idea though. This is how mobile's should be. Simply buy a data plan, no flagfalls or per minute rates or things like that. Of course the telco industry is hardly going to let go of that little cash cow anytime soon are they. But it is the way of the future, I guess we'll get there eventually.