Leaver’s Law: “Everything the system does FOR you, the system also does TO you.”
I first heard this term coined by Don Leaver, one of the best “crusty C hackers” I’ve ever met. He got his start grinding out high-performance unix code, and these days he’s writing (if you can believe it) high-performance Windows code. (Seriously, the man is terrifying. His idea of a good time is making Windows completely surrender one of its CPUs and control of the USB bus so he can process signal data from a mission-critical device without fear of the operating system “taking the app out to lunch while my data puddles on the floor”.) As he modernized from simpler to more luxurious operating systems, this was his lament: that luxury is merely the upside of complexity, and when you gotta get crap done, complexity is the downside of luxury.
I have found that this law is not limited to operating systems, but can be applied to just about anything. I have quoted this law (usually with a curse) at everything from web frameworks to the automatic timer on my car’s headlights.
Leaver’s Law. Now you know.
Why, Dave, Why 
[Edit: When I moved my blog to WordPress.com, it looks like the anonymous comments were chopped out. In fairness to Don Leaver, he posted a reply stating that he couldn’t take credit for it, because he’d heard it from one of his mentors, and that at the time it had been almost exclusively applied to the inner workings of automatic transmissions in cars.]
Don, thanks but I’m still calling it after you. “Leaver’s Law” has a much better ring to it than “One of Don Leaver’s Mentors’ Law”. 🙂 But yes, noted that this is one of those bits of wisdom that just sort of seeped anonymously out of the smartosphere and one day we realized it had always been there.
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