Social psychologists have known for decades that, if we reduce our sense of our own identity ? a process called deindividuation ? we are less likely to stick to social norms. For example, in the 1960s Leon Mann studied a nasty phenomenon called "suicide baiting" ? when someone threatening to jump from a high building is encouraged to do so by bystanders. Mann found that people were more likely to do this if they were part of a large crowd, if the jumper was above the 7th floor, and if it was dark. These are all factors that allowed the observers to lose their own individuality.

Social psychologist Nicholas Epley argues that much the same thing happens with online communication such as email. Psychologically, we are "distant" from the person we're talking to and less focused on our own identity. As a result we're more prone to aggressive behaviour, he says.

Another factor influencing online communication, according to Epley, is simply the risk of miscommunication involved with text-based messages, which are inherently more ambiguous. At the same time, he notes, email "has the feel of informality ? we just fire something off", even though we probably ought to treat it with the same care as a written letter. And, as most people probably know, this can cause problems for both the sender and the receiver.