This post is pure speculation and I have no evidence of this. I do know that GGs engineers are very smart and wily...
If you were a GG engineer and you were concerned that people in the SEO industry were fooling around with your well orchestrated system of ordering results, what would you do?
Take steps to counter that threat.
I would think that pure algorithm complexity is not enough. Eventually, every shift you make would be caught by the community, and while it might take months to be recognized and introduced, with the industry growing so quickly thanks to the money that can be made off of top rankings, you're in a lose-lose situation in the long-run.
So, to counter the threat, you produce a tool that watches SEOers for you - the GG toolbar. It tracks what websites everyone visits, how long they stay, etc. You know that SEOs use this toolbar, especially because you've included pagerank into it. Other factors can help you flag and identify SEOers too - multiple searches for the same term all the time, constant visits to a site and the sites that link to it, etc.
So, you could (I'm not saying they do - it's too conspiratorial for me) flag SEOers and flag their 'Primary Sites' - the sites they search for a lot and make requests about a lot, etc. They could then discount the value of any links that are built on pages that those SEOers visit... mkaing our job a little tough.
What do you all think? Don't worry I know I'm crazy
