Seems like it would be fairly trivial to find any instance of a phrase similar to "this domain for sale" on any page and flag it for human intervention. Because that's how squatters get buyers, right, by indicating the site is for sale? Am I missing something obvious?
Additionally, as a web developer, when I see squatting on a domain I want, I will be absolutely livid. Give me a place to report squatters and I'll happily help you crowd-source what was previously a Hard Problem.