Two of my machines were rebooted today -- unfortunately, one of them is the box that hosts DNS for all of my machines. What a blunder that turned out to be, as named did not come back up after the reboot. As a result for nine hours I lost around two million pageviews until I got home tonight and was able to restart the DNS.
Sloppy sysadmin work on my part, I should have had the rc files tested and working properly.
Also highlights a need for a little DNS redundancy with the level of traffic mine deals with.