Shaddows - 3:09 pm on Aug 3, 2009 (gmt 0)

All in, that sounds like its a folding methodology "yo-yo". As if Google doesn't know what combination of results would most satisfy the searcher, and is trying different resolutions. Presumably metrics such as "% requiring refinement", "no click, new search" and other criteria that us webbies wouldn't be able to record but that express user dissatisfaction would be used for this.

If anything, I'm surprised by the 'stability' of your site on SERPs- it only occupies two positions. Indeed, most yo-yos reported are against otherwise stable results. Yours is against chaotic results, and sounds more like stable churn (forgive the oxymoron) than the standard Yo Yo.