I just came across a good outline and commentary on search arbitrage. Jeremy Luebke at Marketing Pilgrim outlines the different definitions and methods of search arbitrage. If you’re doing PPC search marketing or optimizing your site for search, you’ll want to check out this post.
He raises a great point – is Google not putting an end to this because they enjoy the additional revenue? My experiences at my company lead me to believe that Google can end some of this, but they’re not.