I've only been on the other side of this, but I feel like there are times I've hurt myself as a candidate with the work/life question. Some employers are looking for (and paying for) people who will put the job above everything else. With them, "work/life balance" might be a dirty word. In hindsight, I would phrase the question more like, "what kind of schedule would a successful [person in this job] at your company keep?"

On the other hand, unless you really don't care about having a life outside of work, it's probably better to get rejected by the kind of companies who will reject you for asking the question.