The carrot is stronger than the whip.  I like systems that reward positive contributors rather than those which attempt to punish abusers.  I think stack exchange does a great job with this.  I've not seen a particularly good system for forums yet.

At the end of the day, however, it comes down to who uses it.  Since bitcoin was advertised as a way to make a quick buck (I quadrupled my money in one week), a high percentage of the new members were uninterested in the culture of bitcoin or how it works.  This led to a rapid decline in the quality of posts IMHO. 

I admit to discouraging open discussion of topics which are deemed illegal under various governments when I first started posting.  This was mainly a tactical idea I had for sneaking in under the radar.  In retrospect myself and others like me probably pushed away a lot of the quality posters.  Oh well, hindsight is 20/20.