I've been building up for a blog-rant over this issue for weeks...
"Windows recently downloaded and installed an important security update to help protect your computer. This update required an automatic restart of your computer."
That's the message you get when you leave your Windows machine sitting overnight, when Windows has downloaded something _really_ important, shut itself down, and wiped out all the work you had in progress. VERY annoying.
As I was getting ready to write this, I did a quick Google search for the phrase, and found this entry explaining how I might actually be able to prevent this problem from happening again! Hoorah!
It's also nice to see that there are people out there WWAAAAYYY more angry at Microsoft than me over this (read the comments under that post for some examples).