For values of Europe equal to: the UK, and France, Poland, Austria, Denmark, and Portugal in beta.
Obtaining phone numbers in every country is a bit of a tricky legal process. If we waited until we had all of Europe lined up it would take quite awhile and that wouldn't be very "lean" of us. What if it turns out nobody wants to buy numbers in Croatia but we spent a bunch of time trying to get numbers there?
In the end we will roll out incrementally as we bring on new carriers and forge new relationships in other countries in Europe.
If I recall correctly, even the original iPhone was rolled out country by country, or at least groups at a time, and Apple certainly has a lot more resources than a startup.