The thing is you probably have obvious weaknesses in terms of a mismatch for the posted job description. I don't want to know that you are a compulsive alcoholic, I want to know that you don't have much experience with databases, that you recognize that we want you to use databases, and that you have a plan for overcoming that. Trust me, the interviewer is not going to be unhappy that you said your greatest weakness is inexperience with databases. It is obvious from the context that they are talking about your greatest weakness - with respect to taking this position - If you have agoraphobia following a sexual assualt it is not what they are talking about.