The other day, my car overheated -- pegged the temperature gauge -- after about 5 minutes of driving. I limped it home and discovered it was out of engine coolant. After I added more I could drive for a few minutes but again it violently overheated and all the coolant was gone. With visions of expensive repairs dancing in my head I took it to my neighbourhood mechanic.
It turned out to be a cheaper repair than I expected, but a more frustrating one. You see, the minivan I was driving has a separate heating system for the back seats. Their own controls, vents, everything. We actually use this perhaps once a year, it's a low-value frill. But here's how it works: they pipe the engine coolant halfway back the car so it can go through a heat exchanger and warm up the air in the back. And of course it makes cars easier to build if all the pipes and wires are underneath the car. Over the years, kicked up stones and gravel weakened this coolant pipe until it finally broke, spewing precious engine coolant all over the road. I could have easily lost the engine or been stranded hundreds of miles from home. And for what? A separate heating system in the back? Who cares?
What could they have done instead? They could have piped the hot air instead of the hot coolant, so a leak would only make the back seat cold instead of ruining the car. (I know, from my former life as a chemical engineer, how much easier and cheaper it is to move liquid than air.) They could have installed a sensor that would detect low coolant levels directly, instead of indirectly when the car overheats. They could have run the piping in some protective shroud. (Ha! This is the company that blames me when the wiper motor breaks because the car gets snow and ice on the windshield! Three times so far on this van.) They could have skipped the whole feature on the grounds it made the car way too vulnerable for the benefit it offered.
I see a moral in this story for software developers. What features are you writing that turn out to be a heating system for the back of the van?