Suing a Search Engine Because your Ranking Sucks?

Why is it that people have this weird expectation that having a high search engine ranking is some sort of legally guaranteed right? We've seen a bunch of lawsuits recently where companies sue search engines because they're not happy with their ranking.

However here's a twist. Threadwatch points us to the story of a search engine optimizer (SEO) who is being sued by a former client because that client's search engine rankings have dropped below those of another company, who later hired the same person. It sounds like the complaint from the company is that the SEO later worked for this same company and helped "optimize" their rankings so they beat out the former client. The SEO notes that the work he did for the original client was four years ago and they've done little to nothing to continue the process of optimizing their site. The guy also claims that his agreements with companies make it clear that he does not work exclusively with them, and you'd have to imagine that most SEO contracts do not promise specific results -- especially not ones that would last four years after a contract is complete. It sounds like yet another case of a company suing simply because they don't like something, not because they have any real legal claim.