What is the 'data roaming' function for?

[copydeskcat]

I'm in O2 in the UK ON THE 3G iPhone.

I've just noticed 'data roaming' was disabled?

What is it for, what happens if I enable it - and will it cost me money?

CDC

 

[Darwin]

Best keeping it disabled, this won't effect your data plan in the UK, this feature is turned off by default to prevent "issues" when traveling abroad.

Data roaming can cost you dearly, especially if you have the phone set to check email and you browser the web. (atm it's around £3 per MB if you happen to travel to anywhere in the EU, its higher outside.)