A WebmasterWorld thread tells the story of one Webmaster who, a year ago, was doing very well in the Google results. He then took the advice of Google to redirect the non-www version of his site to the www version (ie. http://seroundtable.com/ --> http://www.seroundtable.com/). After doing that, Google dropped his pages from his site. He waited 10 months! 10 months, for Google to get the clue that he wants the www version index, but they never got it. So he decided to drop the 301 redirect he hand in place and presto, he is back in the results, two weeks later, like he was 10 months prior. Wow.
WebmasterWorld members, admins and moderators quizzed the member on what he did and it seems like he did everything by the book.
Just one more tail of Google's canonical URL issues?
Forum discussion at WebmasterWorld.