For me, it is as much the answer as how you answer the question. I look for sincerity and honesty. We are well aware that people move because of personality clashes at work, difficult bosses, or lack of career progression. We (at least I) want to be sure that you were not the problem! They are people who are the cause of problem at work, but they like to paint it like the colleagues are the trouble makers. So I certainly don't want to be recruiting a problem case.

For our area, it is true that the longer you are out of practice, the further you will fall behind in the field, unless you were using that gap time to catch up with technology. For me, I will be impartial to a candidate with a 6 month unemployment gap if he comes across as a earnest and passionate about the area / subject matter.