Originally Posted by potter

Sounds to me like they're saying they usually do some tracking other than just the cookie. But if you set it to more than 3 days, they wont. -- Probably because since they're storing info in their DB, longer than 3 days is potentially too much information for them to be storing.

So, if that is the case. They will ONLY rely on cookies for your referrals. Where as, if a user is blocking cookies. The referrer wouldn't be known.