In general, not just in relation to stackoverflow, sometimes I'm asked a programming question for which the answer will probably be used for good purposes, but there is a chance that it could not be.
Two recent examples which reminded me of some real world questions I've been asked are:
Though I don't believe the intent of the authors of those questions is in any way nefarious, occasionally someone does ask such a question for purposes of aiding a spamming effort, or creating a keylogger. Even though the questioner and answerers had good intent, a 3rd party could pervert those answers to create a piece of malware or a spam utility.
Should we always trust the questioner to use the answer for good? Should we feel obligated to ask the purpose of a question, and how the answer will be used? And how can we prevent answers from being overheard (when asked verbally) or being referenced (when posted publicly online) and then used for unsavory purposes?