Italy, Spain and Switzerland are next up according to a post by Macworld UK.
Spain Telefonica (parent company of O2, the UK iPhone providor) and Telecom Italia Mobile for Italy. The announcement is going down next week in Barcelona at the World Mobile Congress (Feb 11-14) according to their sources.
A third publication, Le Temps, claims that Switzerland will also carry the iPhone on Swisscom by late February. That is for the few people left who don't already have a hacked iPhone.
