'Up Vote' privileges requires minimal karma(2), 'Down Vote' privileges are rather high(20).
Karma is visible only to the owner and the moderators.
Rationale being, people shouldn't be discouraged to post their problems however small or trivial it may sound and others to share possible ideas to solve that problem or existing solutions without any prejudice.
Ofcourse this raises the issue of people not willing to part their karma to maintain forum sanctity, but as of now that's manageable when compared to discouragement from down votes.
