its also a good way to think about it ....
I was thinking more on how to generate traction (adoption) .... let me try to give some perspective from different angels

• 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 ....

Later on, once you have a bigger pool of questioners & answerers ... you can create profiles linked on topics/subject matter experts .... such profiles within a scoring system would provide insight to other users on believability/credibility

I can go on and on but I dont want to make it very long :)