Recently, on my trip to the US, I was pretty surprised that I was able to connect to a GPRS connection and send/receive MMS outside of my "native" mobile area (the Czech Republic). That surprise wore off quickly, as I remembered that Vodafone actually purchased the small mobile carrier I was using (Oskar) recently ... this purchase, which I didn't think was a big deal at first, automatically gave me access to all Vodafone networks and the networks of carriers they have agreements with. Wow, pretty freak'n cool! Last year, when I travelled outside of the CZ, I had to just "give up" my GPRS connection at the border, but it seems those days are long gone (sure, I could have switched to T-Mobile then, but I was happy where I was for the time being).
I guess sometimes, it's cool when a large company gobbles up your smaller one .... :-)