Google Update on 2007-1

During the last week, we noticed the PR on some sites got changed, but I think it's not a real PR update, just a little adjustment on algorithm. Some site's PR dropped to zero, then rolled back after several days. It's said just some changes on some DCs, maybe just reboot. :-) I can't see any obvious update on PR. Most of sites' PR remained, only one PR of index updated to 3. Wish a big dance will be happened in the next two months. So don't believe the PR update on 2007/01, it's just a joke.

Here's Matt Cutts's explain:
A few people were seeing PageRank 0 for their site. There was a small auxiliary push that needed to happen to complement the PageRank push, and that push happened a few hours ago (i.e. Jan 11, 2007). If you were getting stressed, you might want to re-check now. If you never even noticed, well, good for you.