The most common thing you can find in Yahoo! Knowledge+ is stupid question. Some questions are just so nonsense that you can’t help laughing at it.
I’ve seen many questions asking for medical diagnosis and at the same ask those who answer not to tell him/her to go see a doctor.
When I have time, I usually do answer like this: “If Yahoo! Knowledge+ may give you an accurate diagnosis, why do we need any doctor in the world? They should all be jobless."
Then you may also find many questions asking about some extremely easy to find answers, like syllabus of public exams, tuition fee of university, etc.
And loads of questions that query about Christianity. Some of them ask those questions because they think there’s no answer to it and thus by asking the question, he/she may prove that Christianity is but a hoax. Oh, well…
Though I have to be fair, some are asking questions there as they really did try to find the answer somewhere else but couldn’t get any help from those places.
I just know one thing: when I need to search for answers on the internet, I would avoid taking answers from Yahoo! Knowledge+. Those who have been there know how unreliable the so called “best answers" are. Sometimes, the inquirer simply don’t know which one really is the best answer, though there is a correct one provided.
To me, reading and answering those questions is more like an entertainment =P