Re: promoting
Two things: First, the main point of shortening that long URL, is that it will prevent reviews from being removed on Amazon. All that extra stuff has info in it that tells Amazon YOU furnished that link...therefore, giving them a clue you have a personal connection to the reviewer...if they use that link to find your book to review it. So, the URL should always stop following the ASIN number. Not saying don't use Bitly or whatever...but if you don't, I think Twitter shortens it for you. Just don't use the long URL for anything!
Ann makes an excellent point about the URL telling Amazon what it doesn't need to know. I find the shortened URL more convenient - I can remember it! Rather than copy and pasting the long Amazon one. And it gives me feedback on the number of clicks I get when I post on Twitter or Facebook.