Some Android custom Roms are only available in WWE (World Wide English) which is not really a big deal. However there are a few exceptions when it comes to native characters or services based upon your locale.
Since I live in germany, i have a german Amazon account which I use for online purchase including my music.
When downloading AmazonMP3 from the market, the application will check your locale and set the Amazon Shop accordingly. In most cases of WWE Roms, this will be AmazonMP3(US) and you wont be able to purchase MP3s with your native account (DE in my case).
Using morelocale 2 you can manually set your locale to your preferred area and you should be able to use your native provider ignoring the WWE locale on your phone.