I disagree with this post. If you are so personally threatened by someone asking what your weaknesses are, then I guess I understand your reaction. But personally I just view that as another question relating to your experience. For instance, my two biggest weaknesses are time estimates and unit testing (I still haven't jumped on the TDD bandwagon), so instead of being offended or threatened by that, I will explain my weaknesses and what I'm doing to correct them or my views on them.

Everyone has weaknesses, don't run from them, embrace them as an opportunity to improve.