I'd say that a rough breakdown of unusual Yahoo Answers on polls and surveys (the most popular section) would probably go something like this:
Clearly Joking - 80%
Younger Adolescents - 10%
Seemed like a Legit Question at the Time - 8% (this is where the "wolf barking" question would probably fall; wolves actually do bark, interestingly enough, they just do it rarely).
With the remaining two percent or so falling into that murky category of Other, where some speak English only as a poorly known second language, some have serious underlying psychopathologies, some are members of a fringe religion/philosophy, etc.
Obviously those stats are just my own invention based mostly on what I've seen =P
Virtually all of these, I would say, are jokes or legitimate-ish questions with joking answers. I try not to laugh at any that I think fall outside of those categories, though, because I would rather not laugh at people with serious mental health problems. Being here, I can kind of understand how they feel.