I've been so inactive in the free software universe, I feel that my journeyer status should probably be revoked.
How not to impress a non-Linux user:
I was helping a neighbor burn a mix CD from his collection, and I grabbed a GUI tool for the purpose, a program called xcdroast. I generally do things on the command line, but ordering tracks and keeping track of times is a good job for a GUI. Since I rarely burn CDs, I hadn't noticed that I got a kernel parameter wrong (ATAPI support needs to be a module if the SCSI emulation is built in) so I quickly rebuilt. This is a Debian system, so naturally I use make-kpkg.
Writing tracks to the hard disk is time-consuming, so I was generally bored, and started surfing the net and such. Since I had just rebuilt the kernel, I didn't have the ALSA modules installed, so we couldn't listen to the tracks. Just as we were almost through writing tracks to the hard disk, I decided to take a fatal shortcut to get sound going: I installed the alsa deb I had made on my previous kernel build. After all, I had only tweaked one small parameter, right?
BZZZZZZT!
The machine went down hard: although I was able to ssh in from another box to do a shutdown, I might as well have just flipped the switch off for all the good it did. Reboot force-checked all the disks, and hung when it got to the alsa install. A second reboot into the old kernel force-checked all the disks again, after which I was able to edit modules.dep and blow away the offending alsa module directory.
Now, I know that linux is typically solid as a rock, and it's actually difficult to lock up like I did, and that what I did to make it lock up was atypically boneheaded , but I think I scared my Windoze-using friend away from the platform for a good long time.
Oops.