TinyURL.com was accused of something similar. They offered a "link shortening" service. But if you linked to a page on Amazon, they'd wait a few years and the

TinyURL.com was accused of something similar. They offered a "link shortening" service. But if you linked to a page on Amazon, they'd wait a few years and then swap in their own referrer code in place of yours. When confronted, they claimed this was the nefarious work of a third-party to whom they'd outsourced their link-redirecting...