When a post includes a link to the Japan website of Amazon (www.amazon.co.jp; for example
http://www.amazon.co.jp/dp/4140111127), the Stack Exchange server automatically rewrites it to a link to the US website (www.amazon.com) and breaks the link as a result.
Example: The link http://www.amazon.co.jp/dp/4140111127 is automatically rewritten to a link to
http://rads.stackoverflow.com/amzn/click/4140111127, which redirects to
http://www.amazon.com/dp/4140111127/?tag=stackoverfl08-20, which is 404 not found.
I noticed this when trying to fix the link in this post.