Oh noes! MacBook Random Shutdown Hits
I stared in surprise for a moment at the black screen, then turned the machine back on. It started booting, and then turned itself off like before. I unplugged the AC power and tried again. No luck.
Oh, shit, I'm thinking. What about my data? I should have backed up. I'll have to take it in to get it fixed. But I'm going to RubyConf next week!
So I tired taking out the battery and replacing it, and for some reason that worked.
I did a little research and found out that this problem is pretty common with MacBooks. There's a website devoted to the problem, Apple has acknowledged the issue, and some users are organizing a class-action lawsuit. Some guy even got a video of the random shutdown happening at the Apple store (note: for me, the video pauses at 8 seconds. If you skip past that you can see the shutdown).
The problem is apparently caused by a short circuit where some wires melt to the heatsink.
Marc Zeedar suggested
both processors with
yes > /dev/null & yes > /dev/null would
allow him to reliably reproduce the problem, but that didn't work for me.
So far, it hasn't happened again. My plan is to back up my data, take it
to Denver for RubyConf, and then replace it.