Disposing of old questions that are now off-topic
Here's an ancient Stack Overflow question that would really have belonged on UX.StackExchange today; in fact we have our own version of the question already. Since it's kind of a duplicate that way I wouldn't be sure about moving that one in particular.
But more generally, what do we do about old, popular questions that were originally asked on Stack Overflow (or another older site) but now would belong on a different site? Do we leave them for historical reasons or do we move them to maintain the categorizations?