Apple chose AT&T only for the US but by all accounts had visited with Verizon and other carriers. Perhaps only AT&T would give them the deal they desired. Or maybe they made it so sweet that the other carriers decided to back out. Who knows?
The only thing that is certain is that EDGE is much less prevelant in Europe and it is likely that the iPhone released for Europe will have HSDPA/UTMS support.
So why is everyone saying it must be Vodafone OR O2 when it could be Vodafone AND O2?