Anonymity

I'm currently reading The Lucifer Effect by Philip Zimbardo, and he described an "experiment" where he put an abandoned car both in the Bronx and in Palo Alto. The one in the Bronx was vandalized immediately and repeatedly, and the one in Palo Alto wasn't touched (except when someone closed the hood while it was raining, lest the engine get wet). Three people even called the police to report the car as being possibly stolen when Zimbardo drove it away.

His commentary on this "experiment" (it was really a case study, which isn't an experiment) is interesting:

Any setting that cloaks people in anonymity reduces their sense of personal accountability and civic responsibility for their actions. We see this in many institutional settings, such as our schools and jobs, the military, and prisons.

I think he forgot to add "the Internet". This sounds exactly like the constant cries of well-meaning citizens that the internet doesn't foster civil discourse because the anonymity removes people from responsibility for their actions (in this case words). I've never really given much credit to this argument, but there might be something to it.