I never use Ruby's case or switch or whatever-it's-called.
I could make up some mumbo-jumbo about case being a code smell and that it should actually be refactored to a method dispatch over polymorphic objects, but the truth is that I have no idea why I don't write case statements, I just don't.
Add me to the "never uses switch statements" list. I've never seen the point in learning the syntax in any of the languages I know, since a bunch of else ifs (or elseifs, or elsifs, or elifs, depending on the language) does the same thing. If I waste a few keystrokes, but save a few brain cells, I think it's a worthwhile bargain.
Of course if I had to write that kind of construction often I'd probably learn the syntax of the case statement, but in the kind of work I do it hardly ever actually comes up.
It's really just a performance optimization for C, in situations where the switching value can be hashed. In languages that make method dispatch easy, and the overhead of a function call is not something you're terribly concerned about, it makes sense to just roll your own as needed -- that's why Python never bothered with a switch statement.
Ability requires memory, at least for basic things.
You can't be a good programmer and forget the syntax of the language you are working in. If you need to look up something as fundamental as switch statement in the internet, it's like a writer looking up words in the dictionary before writing them down in his novel.
I think switch is a particularly bad example here. Honestly, I can't (accurately) tell you the last time I used one. It's not an every-day construct for a lot of people.