The "I'm not eating that!" thread reminded me of a disaster that happened a few years ago (apologies if I've told this one before).
I was baking banana bread, and I'd set the oven timer for 60 minutes. I then went downstairs to do some chores, and I lost track of time. I thought "Hmm, wonder if the banana bread is done yet", and I poked my head up the stairs. Didn't hear the timer going off, so I went back to what I was doing.
About 20 minutes later, I thought "SURELY it's got to be done by now! Why haven't I heard the timer?". I went upstairs, only to be greeted by black smoke and the awful smell of burned banana bread.
Turned out that my teenage daughter, annoyed by the sound of the oven timer, just turned it off. Didn't turn off the oven, didn't tell me the bread was ready, nothing. Grr.