One thing that StackOverflow does really well is penalize you for downvoting: http://stackoverflow.com/privileges/vote-down http://stackoverflow.com/privileges/

One thing that StackOverflow does really well is penalize you for downvoting: http://stackoverflow.com/privileges/vote-down http://stackoverflow.com/privileges/vote-down Each downvote costs you karma. You have to have "X" karma before downvoting is enabled for your account. This incentivizes you to downvote cautiously as it costs you. That subpar comment you're clicking the down-arrow for must have really earned it.