The most recent spectacular failure happened when interviewer asked about sets, i described Java Set interface as an example (they are Java shop so i thought the choice was right), looking dissatisfied he asked to talk about "sets" in general, and got, lets say, really confused, when i tried to elicit whether he means naive set theory - seeing that i didn't hit what he wanted, i offered along the lines of Russel's theory of types, ... the guy got almost angry and said "just sets in general", and i kind of supposed that we settled on naive, though it sounded like he didn't like "naive"... he asked what we can do with a set, like for example iterate over its elements, i noted that that of course depends on the set's cardinality ... by look on his face at that moment it was really clear that the interview is finished.