IANAL nor an affiliate marketing expert, but if I ran an affiliate program I would make that against the rules. It at least goes against the intent of the program, which is to reward/incentivize people who send you business. Everyone clicking these links was already going to your site, so bit.ly as an affiliate generates zero extra dollars in sales.
Hey I'm just a guy. Maybe Amazon figures it's better to police affiliate links lightly or that a bit of a giveaway to SO isn't such a bad thing. If I ran an affiliate program I probably wouldn't allow that behavior.
