How is this possible? Check this site, please. You are browsing Amazon and you are seeing a different URL at the browser's address box. Is this a violation of Amazon's policy or perfectly acceptable?
Its against their TOS, all they are doing is iframing amazon homepage via their affiliate link check the source code you will see.
All along I was wondering how this redirection became possible. It's a clever idea, but certainly Amazon would remove this account once the company discovers it.