Let me try working through a few variables on this one!

If the interviewee is going to fool a completely competent and prepared interviewer, he's going to fool the SQL forums and get his answers. (I'm obviously mistakenly ommitting the geniuses here who will see through every scheme no matter how sophisticated by the sheer power of their perception, but in that case I'm an ordinary joe that can subsequently answer questions the faker posts because well I'm an ordinary joe and Steves advice does not apply to me in this case.)

If the interviewee is not going to fool a completely competent and prepared interviewer, will he fool the SQL forums and get his answers? If I find him out, I'm going to answer him but tell him it sounds like he wants to cheet and will probably fail because if I'm an ordinary joe unskilled in HR and spotted his dastardly scheme, the competent HR department will surely find him out!

If the interviewee is going to have an incompetent and unprepared interviewer, do we reward incompetence and lack of preparation by refusing to answer questions in order to protect the incompetent and unprepared interviewer? Or might this somehow dilute free market forces that would otherwise penalize incompetence and lack of preparation?

How about the many different degrees of competence on either of the interview participants part? How does that pan out?

Additionally, if an applicant is truly dishonest (and especially good at being dishonest), are we saying he's going to fool the interviewer but not the forum participants? Heck, he's got an easier job fooling forum participants because by definition in his participation here he's not providing answers, he's formulating questions!