This question is not as stupid as it seems. True, your answer will most likely suck if you haven't thought about it previous to the interview, but this is probably true for most of the behavioral part. The interviewer is not looking for a boilerplate answer like "I'm a perfectionist" etc. You have a good chance to demonstrate that you are self-aware and able to recognize your weaknesses and to show that you are worki…
If you are a decent employee a lot of interview/employment stuff will seem formulaic but I have to say I now use more of this kind of stuff after being burnt a couple of times by taking all this boring sort of stuff as given and then the employee turning out to be unsuitable - in both cases at great cost to myself. In both cases they seemed personable and having the correct skills but the problems where much deeper and would have been turned up by probing and cross checking - which is what this kind of question is actually designed for.