tedster - 6:07 pm on Jan 18, 2007 (gmt 0)

I think that the "PR Update" is a red herring here - although the PR shifts did add to people's upset. Historically, a PR update is just a data export, and it's not involved in the ranking calculations. The real PR that Google does use for ranking is updated continually and has been for years.

Matt Cutts blogged about this very point last October during the previous toolbar PR export.