I have found an interesting article here.
It describes how an American family with 3 iPhones received a 4.800$ bill after their Mediterranean cruise even though their iPhones were barely used. How you ask? The costs were generated by data transfer and roaming fees. By having the iPhone set to retreive your Emails automatically the iPhone keeps checking your mail and the transfered data (even though it might not be that high) generates this almost outrages amount of cost.
What do we learn?
- Turn off automatic Email retrieval before you go on a cruise.
- Roaming fees still are outrageous.