"Consider the results from a study where college students who did not know each other came to a lab and were 'virtually' put together in pairs in an online chat room to get acquainted. About one in five of these Internet conversations quickly became startlingly sexual, with explicit terms, graphic discussions of sex acts, and outright solicitation of sex.
But when the experimenter who conducted these sessions later read the trascripts, he was astounded. As far as he had seen while escorting the students in and out of the cubicles, they all had been low key, unassuming, and invariably polite - completely out of keeping with their uninhibited licentiousness online.
Presumably none would have dared plunge into such blatantly sexual talk had they instead been having a live, face-to-face conversation with someone they had met only minutes before. That is just the point: during in-person interactions we loop, getting an ongoing flow of feedback, mainly from the person's facial expressions and tone of voice, which instantly tell us when we are on track and off.
Something like the out-of-place sex talk in the lab has been documented ever since the earliest years of the Internet: "flaming," in which adults make childishly offensive comments online. Ordinarily the high road keeps us within bounds. But the Internet lacks the sort of feedback the OFC [orbitofrontal cortex] needs to help us stay on track socially."
- from Social Intelligence: The New Science of Human Relations, Daniel Goleman
(I guess I read books like this to counteract the damage that all this time spent online has rendered to my non-virtual social abilities)