Do the sysadmins and programmers you are interviewing need to understand the innards of a USB keyboard as part of their job function? If it's not part of their job description, then I am not surprised at all.
If they have the balls to say "no idea, why do I need to know" that is someone we like. If they say that and then attempt to work out an answer extra bonus points. If they stumble they get no set back - it is a random question. If they bullshit they are marked down a fair way - not the kind of person we want.
(we design it to be a question you have to actively fuck up to be marked down on)
We sit and work through an answer together and you get a real insight into them outside their area of expertise (where you would expect them to be slick)
