I'll bite: yes, if there's rapport and the candidate doesn't feel caught off-guard or needlessly pressured. If it's whiteboarding like you'd whiteboard while on the job with your coworkers, that's a good idea that can tell you a lot about a candidate. Unfortunately, in my experience, that doesn't seem to happen very often. A lot of people seem to treat it as an adversarial process or expect, for lack of a better description, a "performance" over contrived problems.

I've had my share of the second kind, which were without exception some of the most unpleasant interviews I've ever gone on.