The Broken Windows theory of crime states that in an environment of disorder, people will be more willing to commit crimes.  If you allow jaywalking and urinating on the street, the reasoning goes, people will feel licensed to further offend against the public order.  The theory was first popularized in our very own magazine, and became a favorite of Rudy Giuliani's police department.

It's fallen somewhat out of favor these days, as a lot of people question its empirical grounding.  But the Economist reports on an experiment that seems to show some support for it:

The most dramatic result, though, was the one that showed a doubling in the number of people who were prepared to steal in a condition of disorder. In this case an envelope with a EUR5 ($6) note inside (and the note clearly visible through the address window) was left sticking out of a post box. In a condition of order, 13% of those passing took the envelope (instead of leaving it or pushing it into the box). But if the post box was covered in graffiti, 27% did. Even if the post box had no graffiti on it, but the area around it was littered with paper, orange peel, cigarette butts and empty cans, 25% still took the envelope.

Interesting to think that "too pretty to steal" might be an actual defense against crime.  Kottke goes further, and wonders if there isn't a broken windows theory of internet trolling:

Much of the tone of discourse online is governed by the level of moderation and to what extent people are encouraged to "own" their words. When forums, message boards, and blog comment threads with more than a handful of participants are unmoderated, bad behavior follows. The appearance of one troll encourages others. Undeleted hateful or ad hominem comments are an indication that that sort of thing is allowable behavior and encourages more of the same. Those commenters who are normally respectable participants are emboldened by the uptick in bad behavior and misbehave themselves. More likely, they're discouraged from helping with the community moderation process of keeping their peers in line with social pressure. Or they stop visiting the site altogether.

Unchecked comment spam signals that the owner/moderator of the forum or blog isn't paying attention, stimulating further improper conduct. Anonymity provides commenters with immunity from being associated with their speech and actions, making the whole situation worse...how does the community punish or police someone they don't know? Very quickly, the situation is out of control and your message board is the online equivalent of South Central Los Angeles in the 1980s, inhabited by roving gangs armed with hate speech, fueled by the need for attention, making things difficult for those who wish to carry on useful conversations.

There's definitely an imitative component, because I get waves of trolls who repeat each other, presumably mimicking some ur-troll I haven't seen.  This is most readily apparent when, as happens about 50% of the time, the ur-troll has (deliberately?) misread the post in a totally unsupportable way, and his minions make asses of himself repeating the accusation without themselves reading it. 

So how much of it is monkey-see, monkey-do?  And how much of it is a spontaneous outflowing of nonsense?