Questioner (person asking): the intention of any questioner does vary (looking for social interactions, truth, entertainment etc...) so we can never tell what that is, therefor letting the system decide which answer is best is probably a good way. at the same time, its also useful to have the questioner decided which one is the best answer as it can be purely subject and personal (how the questioner feels about the answer)

Answerer (person answering): intention is also unknown and varies but in general the answerer wants provide input .... a mechanism to reward/punish needs to be in place to encourage answers the questioners like ....