Nick W reports that Google is testing a pilot program that emails webmasters to warn them about pages that contain techniques that violate their guidelines.
Dear site owner or webmaster of [url removed],
While we were indexing your webpages, we detected that some of your
pages were using techniques that were outside our quality guidelines,
which can be found here: [link]
In order to preserve the quality of our search engine, we have
temporarily removed some webpages from our search results. Currently
pages from [url removed] are scheduled to be removed for at least 30 days.
Full letter at Threadwatch.