I was among the first to order the Kindle 3 as soon as it came out. Because it wasn’t available in Germany, I ordered it straight from US with my amazon.com account, despite having to pay lots of extra fees. The Kindle device was linked to my .com account and, despite some disadvantages like paying a small fee because of the $ to euro conversion, I also had the advantage that I could borrow books from all the nice people from US who were willing to lend it to complete strangers on lendle.com and booklending.com. Back then people in Europe couldn’t lend book, we still can’t and it’s uncertain when this feature will be enabled. But at least we could borrow books from others.
One month ago Amazon finally added the Kindle device and books on the German site too. I received a notification per email and also every time I browsed on amazon.com saying that I should switch my Kindle account to the German version to benefit from all the cool new features, like paying directly in euros and being able to buy books in German too. I wasn’t so interested in German books since I read mostly English books but not having to pay that conversion fee was pretty tempting. So without giving it a lot of thought, I did what most probably did as well, I switched my Kindle account from amazon.com to amazon.de. So far so good… I continued to buy new books for my Kindle but with the exception that it was from the German site from that point on. What I missed the most was the reviews of the English books but I could live without it.
Because I got a few books which are lendable and I marked them as owned on lendle.com, I had the possibility to borrow books again. As soon as I placed a request for a book I wanted to read, someone on lendle.com was willing to lend it to me. As I went to amazon.com to claim the book, I was shocked to see that I’m unable to do it. My Kindle account is now ported to the German amazon site so I’m unable to use any of the features provided by the US site. If I would’ve known this upfront, I would’ve stayed on amazon.com, at least until Amazon finally enables borrowing and lending for customers in Europe as well.
FitGeekGirl 
Have you tried to switch your account back to .com? Was it possible? I actually just need one book from the .de store but don’t want to leave .com because I have some subscriptions and want to enjoy a greater choice in English books.
I searched for ways to switch back from .de to .com but found unfortunately none.
According to Amazon, your Kindle account must be in the country where you live. If you want to switch to the Kindle store in a different country, you must prove that you live there by providing copy of your ID and lots of other documents. Sometimes this is not even enough because Amazon is checking from which country you are accessing the Kindle store by verifying your IP address and if it’s from a different country than the store, they’re going to contact you to move your account back, wheather you want it or not. This is all because the books have different prices in every country.
So if you want to stay at .com, then don’t switch at all. It’s not worth it. Try to buy the book from another store in electronic format, convert it to the Kindle format and copy it on your Kindle. It’s sounds complicated but it’s the easiest way.