suzukik - 11:08 pm on Apr 18, 2012 (gmt 0)
Matt Cutts says on Google+ [plus.google.com]:
I saw a recent post where several sites were asking about their search rankings. The short explanation is that it turns out that our classifier for parked domains was reading from a couple files which mistakenly were empty. As a result, we classified some sites as parked when they weren't.