I think it's a misidentification of the reason why a certain class of proposed solutions to social problems do not work. The class consists of solutions which fail to take into account that people will change their behaviour as necessary to achieve whatever their purposes are, and will simply step around any easily-avoided obstacles that may be placed in their way.
The famous picture that Bruce Schneier once posted as an allegory of useless security measures, of car tracks in the snow going around barriers across the road, is an excellent example. "The Internet routes around censorship" is another.

(from The Weakest Link)
That seems like a plausible story! And was also the message I was pointing at here.
The recent implementation of a -5 karma penalty for replying to comments that are at -3 or below has clearly met with some disagreement and controversy. See http://lesswrong.com/r/discussion/lw/eb9/meta_karma_for_last_30_days/7aon . However, at the same time, it seems that Eliezer's observation that trolling and related problems have over time gotten worse here may be correct. It may be that this an inevitable consequence of growth, but it may be that it can be handled or reduced with some solution or set of solutions. I'm starting this discussion thread for people to propose possible solutions. To minimize anchoring bias and related problems, I'm not going to include my ideas in this header but in a comment below. People should think about the problem before reading proposed solutions (again to minimize anchoring issues).