According to the Adwords blog, Google is updating their automated process for weeding out crappy landing pages. Here's a blurb from their blog post:
From time-to-time, we improve our algorithms for evaluating landing page quality (often based on feedback from our end-users), and next week we're launching another such improvement. Thus, over the coming days a small number of advertisers who are providing a low quality user experience on their landing pages will see increases in their minimum bids. It is important to note, however, that the vast majority of advertisers will not be affected at all by this change, as they link to quality landing pages.
Basically, they're trying to get rid of some of the junky made-for-adsense and affiliate landing pages that clutter the Adwords results. It's not clear (to me) exactly how they evaluate the quality of a landing page, but they do provide a set of guidelines for landing page quality.
I think relevancy is a good thing to check for--by that I mean, does the ad copy accurately describe the content of the link that will be clicked on--but who's Google to decide the quality of a landing page? They can't fairly base it on the amount of content. A page with 5 words might be exactly what I'm looking for even though it doesn't contain a lot of robust and unique content about the topic. This is PPC ads we're talking about, not organic search. I don't know how much they can filter sites out without taking a serious cut out of their revenue because those junky pages are all I see on a lot of search results. If you want quality you click on the the organic listings, if you want to buy something you click on the adwords links. Am I right?