According to Matt Cutts, “We periodically receive updates to that list and received one such update to release on the site this morning. Unfortunately (and here’s the human error), the URL of ‘/’ was mistakenly checked in as a value to the file and ‘/’ expands to all URLs.”
So let’s see now...one worker at Google mistakenly types in a ‘/’ in a URL, and shuts it down for almost an hour?
That’s not good!