I think 3-5 is a good number. I do realize that there has to be a limit or you'd have trolls and fetishists spamming the entire place with duplicate, similar, or completely inane questions that would clog up the feed. Sort of like Yahoo! Answers has the askers who repeatedly ask questions that are practically the same but have a few minor details that are different, and they seem to do it for arousal (they are usually fetish-related questions about feet, hair, armpits, etc.).
People are asking too many questions these days and a lot of other questions are getting overlooked. I think 3 is a good max. There are a lot of users and there are a lot of unanswered questions. I think it should stay this way.