I wrote about Amazon's MP3 service only working for USA-based customers last year, and since then I haven't had to deal with them.
Lady Gaga's new album, Born this Way, is available on Amazon for $0.99 for a limited time. iTunes has the same album for twelve bucks. This is a financial no-brainer—but I can't buy it with my Canadian Amazon account (even though I'm sitting here in the USA right now...).
I think discounting something over ninety percent on one venue and not another is awkward and foolish. As someone who likes buying things from the iTunes store (now that it's no longer DRMed!) I would be perfectly happy to buy it there, but I am not willing to pay such a premium.
But there's a nice workaround: From my Canadian Amazon account and spending Canadian dollars on my Canadian credit card, I can buy Lady Gaga's album—they'll take my money!—and give it as a gift to someone with a USA-based Amazon account. They'll take the money but still don't think I should have the rights to the files!
There are numerous ways to transfer MP3 files between individuals once they are retrieved from Amazon, of course.
As a bonus, my subterfuge rewarded me with a free upgrade to 20GB of cloud storage at Amazon. I have no idea if I'm ever going to use it, but free is free.