You really couldn't make this up. Following reports that the T-Mobile G1 Android phone could not operate at all without constantly using its internet capability - at least, not for US customers roaming overseas - I chased T-Mobile here in the UK to see whether this was the case here. The implications for data roaming bills are, of course, significant, as has now been shown.
Today I get this following nugget from T-Mobile UK. It does not specifically address my request for confirmation of the problem in US models, but it sure confirms it by implication:
In order to ensure that customers do not incur unexpected costs, roaming is disabled on new UK G1 models. There is an option which allows users to enable roaming, but when this is selected the user will receive a message to confirm that there will be additional costs incurred. At this point users are then given the option to either go ahead and enable roaming, or to cancel.
So, just to recap: "new" UK models of the G1 (does this not apply to the very first models released here?) have roaming disabled. Not just data roaming, but all roaming. You can't use the phone outside the country, unless you activate all roaming, including exorbitantly-priced data roaming. It's all or nothing. Who thought this was a good idea?