Reading the Vodafone T&C's tonight, including gems like: "Any SIMcard we issue to you remains our property. You must return it to us in good condition when your connection ends. We may charge you a fee if you fail to return the SIMcard within 30 days after disconnection."
WTF?! Do phone companies really expect to get that SIM back? When I visit a country I usually buy a SIM if I'll be there for more than a few days in order to get a data connection, and then I leave it behind on my way out of the country.