Tony Curzon has written an excellent Open Democracy piece on how auction theory suggests that Google should evolve PageRank in the light of rampant SEO.
I've thought for a while that the equivalent would be for Google to give you not your own PageRank as a score, but the PageRank of your next closest "competitor", or web site. You could then SEO all you like, it won't affect your PageRank, except in so far as it affects your closest competitors'. The trick in this scheme will be implementing who your "nearest neighbour" is for any web page.
Auction design is hard, and things can go badly wrong when faced with cunning and potentially collusive players. Both black and white hat SEOs are cunning, and increasingly collusive.
No wonder Google is stocking up on game theorists.
