1. I saw a question on a JavaScript newsgroup or forum, which was essentially "how do I get checkboxes to behave like radio buttons?" -- how to get a set of checkboxes where if one gets checked, the others become unchecked.
   
   Three or four people gave solutions -- it's not hard to get an array of all checkbox objects and check or uncheck them programatically in JS -- but only one said "that's a terrible idea! Checkboxes are checkboxes and radio buttons are radio buttons. You will upset and confuse your users if you do this". That's a much better response than just telling them how to do it, because they've misunderstood something fundamental, or they wouldn't be asking.
   
   
2. I often see on PerlMonks a kind of intermediate variety of this problem. It's not "how do I do (something stupid or dangerous or wasteful)" it's "I want to do (something quite sensible-sounding) and I've already determined that I'll do it such and such a way, and I'm stuck, please help me".
   
   It's like someone's written "I want to get a screw into some wood, but my hammer's handle is slippery, what shall I use to make the hammer do the job better?" and you have to say that a screwdriver is the correct solution. And probably just as often, the person asking says "I want to fix two bits of wood with one of those metal things, which hammer should I use?" and you have to encourage them to explain whether it's a screw or a nail in a follow-up post.

“Every bit of code is either naturally related to the problem at hand, or else it's an accidental side effect of the fact that you happened to solve the problem using a digital computer.”
M-J D