Brian Marick drew my attention to Jason Yip's take on Gilb's Law. I agree that this corollary deserves equal status.

(Yip's comment is also a fabulous demonstration of the power of few words. Compare it to my blog from last year on roughly the same topic. Yip uses less than 20 words to say the same thing, more powerfully, that I said in about 300. *sigh*. Must remember: minimalism.)