Receptional_Andy - 9:19 pm on Nov 4, 2008 (gmt 0)

I placed the affiliate link once more, and the article disappeared. It was ranked #2 this time. I won't remove the affiliate link. I'll keep it and see what happens.

As Tedster said, be very careful about assuming causation, and also about how you view your test. Essentially, you're conducting a different test now, on a page that is adding and removing affiliate links, and make other minor changes frequently ;)

Also remember that the fact the rankings have been so unstable means this page is unlikely to be highly "trusted", and hence is more subject to ranking fluctuation - both because of changes you make, and changes Google make - as has been happening recently.