I always tell people that if it's worth memorizing because you use it a lot, you'll probably memorize it because you use it a lot anyway. If you have to make a point to memorize something, it's a hint to consider if it's worth the time.
I don't think people should put in effort to memorize things like command line switches. The issue I'm arguing against is accepting that we must now google everything to get work done. I agree that if its worth memorizing, you should eventually commit it to memory through repetition. The problem is that sometimes this doesn't happen. This is a sign of a problem, likely with the interface you're interacting with. If we accept the expectation is to just google everything, no one will ever stop to ask whether the interface itself is broken. If we accept that one should develop a mastery of their environment over time, then incentives form to improve ease-of-use, elegance, and "memorizability".
