martinibuster - 10:31 pm on Aug 31, 2002 (gmt 0) This is done to ensure a less static serp.
My theory about the bouncing serps is that the variables in the algo change from month to month. Indeed, I believe that the algo can actually change week to week. The changes will place a heavier emphasis on a particular aspect of optimization, i.e. title, links, etc. So if you have a site that is optimized in a balanced manner, covering all the bases, then you should be relatively stable. Whereas if you slack off on say, keywords in the directory name, and that's got a heavier emphasis this month, you're out of luck.
This is done to ensure a less static serp.