I try to always select one but I find it hard when I ask questions that ask for answers which are subjective. In that case sometimes I just pick a funny answer or something I really agree with and/or they put a lot of thought in to their answer.
I assume a lot of people just don't care so they don't ever do it or they are waiting for more answers, or maybe they just forget.
I'm a little guilty ..but do try and go back and pick best answer
I think waiting two weeks is good because it is really easy to find answers after a few days picking in less than a day is ridiculous unless only one person answered and they cleared up everything a qa was concerned about
I think that's a good idea, too - about the prompt. They should be reminded after their question has been posted for a certain amount of time. I think toulose gave the most common reasons most of us might not want to choose best answers so quickly. I think I tend to be more determined to find a best answer depending on how urgent my question is.
It might be that xper point hunting has turned into a game for many of us, but for those who actually ask questions without xper hunting as a basic drive it simply doesn't occur to them that selecting a best answer will make a difference.