When a user flags somebody there should be a box that appears below saying Why are you flagging this person. The box should have a place to answer and submit also there are limited choises on what you can put in the box.
A question needs 5 flags to be hidden. If 5 diffrent people flag the same question there must be something wrong with it. (Except if it is a duplicate account and those are banned as soon as they are noticed). It's not such a big deal if you get 1 or 2 flags. And as fondant said "If something's flagged, it should be obvious why it's flagged."
///Jofly