By the way... I referred to the ads as being part of a "rotation." Thinking that through, I realize that probably wasn't the best choice of words. The ads are displayed using pseudo-randomness - I say pseudo because computers are rarely random (except for Windows lockups and crashes - but that's another story altogether). The ad code generates some randomness and then yanks an ad based on the result. The more ads we have, the more "random" the results will appear.
-cec