For example, there are Webmasters that are blatantly using their landing pages for click arbitrage, and Adam posts two such examples. These landing pages host nothing but sponsored
links (likely from AdSense or the Yahoo Publisher Network) and force users to either hit the "back" button, dive deeper to find real "quality" content, or click on a sponsored ad--and possibly be
directed to a similar, spammy page.
All in all, it's a poor quality experience--exactly the kind of experience that the Quality Score is supposed to prevent users from having.