Have you really had people answer "I don't care" to an interview question? I've done a lot of interviews and I don't think I've ever heard that.

My impression is that mistakes due to floating point issues are usually due to ignorance (not understanding floating point nuances) or oversight, or due to an incorrect judgement call that it won't matter. (And really, I think that in the vast majority of situations, normal float math is fine. The backend should be doing the important math anyway.) "Automatically fired" seems very harsh in these situations, or even the situation you described.