Can't speak for everyone else, but I know that for me, I only answer a question to which I have knowledge, and even then, it must be worded correctly. There are a ton of vague questions out there, and questions about how to beat drug tests, (how fast can vinegar clean me out), how different chemicals get you high, unique relationship questions (how can I get this boy to like me), and the such that I just stay away from, because they are unanswerable, or just dumb. I also do not answer questions that are the obvious exact question on your homework or exam. Not my job.
Ask a simple, direct, detailed question, and you will more than likely get an answer. Kinda like this one...