It seems that customers aren't the only ones being confused by Amazon's new geographical restrictions on Kindle editions. I had the following interesting series of events happen (disclaimer: I am a US resident - always have been):
On Saturday I visited the Amazon website to check on the price of the Kindle edition of "Midnight Fugue" - and was informed that it was NOT available for purchase in the USA. On Sunday it was miraculously available for the USA.
OK - odd - but I thought I might have somehow been directed to a UK edition through a bad link.
Yesterday (on a different PC) I went to buy "Shadows Over Baker Street" - which I had on a wish-list for months. The web page had the "Not for sale to residents of USA" warning on it - but it did offer to send me a sample. So I got the sample, and then on the Kindle used the option "Buy this book" and purchased it via my Kindle. I backed up a copy on my PC and saw it had the file extension .azw.prc. Today the book is again available on the Amazon website for US buyers. I've never seen the "Not for Sale" warning with the "Download a Sample" option before.