Having recently launched an affiliate program, I'm interested in how other sites may use some subtle methods to shave.

For example, I know not all sites measure conversion rates from the landing page. I've heard some even measure from hits on the Join page!

I also saw one site that told webmasters that cookies were unreliable so they use session IDs instead...meaning you only get credit if a vistor signs up on the first visit!

Any other observations or experiences?