Even more, if they know my address (since I'm a repeat customer and am logged in) and they won't ship some items to me because of my country - is it really too much to ask to mark those items clearly in the item selection? And filter search results based on which items I can actually buy?

Even Amazon currently just says "can't ship to this address" at the very end of checkout. What am I supposed to do at this point of web interface - quickly move to another country and then input the new address?