t-Mobile (from U.S.A) has just announced that their wi-fi service/account will be available overseas. i.e. If you have a wi-fi plan with t-mobile USA, your account allows you to use wi-fi from their european locations. That information is very hard to find on their site. It is described here. I happen to have a t-mobile account that I use while travelling, in American Airline airport lounges, and I am in Frankfurt right now. So I headed down to one of the hotspot equiped Starbucks, to see if my account works.
Well, yes and no. For the last two months Starbucks/t-mobile are running a promotion. Wifi access are free. When I try to sign on with my own ID instead of the "free" guest ID, it did not work. But the free ID worked so I still get network access. I will try again next month when the free period is over. (I must be the only one wishing the promotion is over...).
Update: It works !! You need to append @t-mobile.us to the user ID.