As a general rule of thumb, I try to match the amount of effort that I spend on answering a question to the (perceived) amount of effort that the OP has put into asking it. Of course, this isn't always appropriate. It just depends. A bit like kyle, it usually depends mostly on me™ - how much free time I have, how interested in the problem I am, how appropriate/complete existing answers are, what I had for breakfast (or not) that morning, etc.

Although I do try to keep the aphasia factor in mind (thanks, Buk), I tend to find poorly worded and/or presented questions annoying. But I generally try to do my best to ignore these and let others deal with them.