Bentler - 2:39 pm on Apr 10, 2007 (gmt 0)

If it was based on traffic alone, indeed it would be a "rich get richer".

From what I've seen, G will periodically drop a page-- some say penalize it in response to a spam trigger but the end result is the same. I think this is when they sample the traffic in earnest; if the dropped page continues to get traffic because of the page's natural importance, it will bounce back in the serps. (speculation, based on personal observations) No traffic? Supplemental.

So even the rich can get fluxed if they hit a bad traffic cycle, and such a sifting design would tend to open up opportunity for new pages to get traffic for an algorithm to use for comparison. I think of it as active experimentation on their part. I think the other search engines are sensitive to traffic too though, which would tend to dampen the sifting and shore up the rich pages, and so it bears out that the ones that perform well in other search engines and that buy advertising will likely maintain position.