I'd think it would depend on the circumstances under which one asked, but also on the person's reason for asking.
For example, if you're on a first date (or with someone you may see as "potential dating material"), that kind of question can just be part of a sincere effort to get to to know the other person better (or else to come up with stuff to have a conversation about).
On the other hand, if people happen to be at the same party and just happen to be talking, I kind of think it's better to let the person share what he wants to share. That approach may eliminate some "fuel for conversation", but under those circumstances I think there are other things to think up as "fuel for conversation".
Circumstances, motive and maybe a "need to know" basis seem to me to be good guidelines.