When you are abroad and you use your own AT&T locked iphone (not iphonetrip.com iphone) then your data roaming switch is off. It is better be this way, because otherwise you just can encounter enormous data roaming charges. It also means that you can not post tweets from anywhere like you are used to do in the USA using AT&T 3G internet. So, how you still make posts on twitter and how much it could cost you ?

You can post by sending sms to local twitter number. Because you are outside of USA each sms will cost you $0.5, meaning if you do 15 twitter updates per day on average and you travel for 1 week you will pay total $52 just for updating twitter. When you are traveling there are so many new exciting things you want to tweet about, to remember, to let your friends know so why to limit yourself? Just use iphonetrip.com service and you have unlimited twitter capabilities everywhere and thousand other things you can do from iPhone. Happy traveling with twitter!