''[I've] found that I can be drawn into ridiculous pissing matches online in ways that just wouldn't happen otherwise,'' the American high-tech visionary writes in his 2010 book, You Are Not a Gadget.

But Lanier and his tech-savvy peers aren't the only ones at the mercy of this creature. Sometimes it turns the most sensible, considerate person into a toxic tyrant hidden behind the safety of a computer screen.

High-profile victims, such as television host Charlotte Dawson and NRL star Robbie Farah, have generated headlines in recent weeks but bullies don't restrict their prey to celebrities.

For Lanier, part of the problem is the mob mentality of web culture.

Psychologists also have a few theories about the motivations of our ''inner trolls''.

They come down to two main arguments, says a professor of social and political psychology at Murdoch University, Craig McGarty.

The first suggests online anonymity frees people from normal social constraints, which emboldens them to do nasty things they would never dare if they could be identified.

The second theory argues that online anonymity doesn't necessarily turn people into jerks. Rather, it liberates them to take on new identities - good and bad - depending on their audience and which online groups they identify with.

Aggressive behaviour can get out of hand on the web because people lack the usual facial cues or gestures to tell them what they're doing is hurtful and they rarely suffer consequences for poor behaviour.

A senior clinical psychologist at the University of Technology, Dr Rachael Murrihy, says online bullies often minimise their behaviour as joking or teasing.

''They often don't acknowledge the seriousness of what they're doing,'' she says. ''It's often motivated by boredom, to get a rise out of others … or by jealousy.''

This was true for Sam, a 20-year-old university student from Melbourne who once bullied schoolmates to impress her ''cooler'' peers. The otherwise ''completely normal kid'' started taunting people face-to-face but quickly moved to anonymous methods via phone, email and online messaging.

''It kind of felt acceptable and fun because everyone with you was egging you on,'' she says.

''Afterwards, if you saw the kid the next day and they were sitting by themselves, you'd feel guilty but … there were definitely times when it didn't even cross my mind or bother me.''

A Sydney-based researcher and the co-author of an upcoming book on cyber psychology, Karyn Krawford, is investigating whether some cyber bullies suffer a lack of empathy resulting from internet addiction.

''If you spend too much time on the internet, it actually unlearns the empathy you may have had at an earlier stage,'' she says.

For Sam, the turning point came in year 8 after she herself was bullied and when her mother caught her hacking into a schoolmate's email. ''She got extremely angry and … sat me down and we had a really big chat,'' she says. ''She said, 'You're doing exactly to these kids what they were doing to you … Why would you do it when you know how it feels?'''

A history of hate

❏ April 2006 The parents of American teenager Mitchell Henderson are hounded after their son commits suicide.

❏ March 2011 American singer Rebecca Black receives death threats after the release of her YouTube pop video, Friday.

❏ August 2012 TV host Charlotte Dawson is hospitalised after Twitter trolls tell her to ''please go hang yourself''.

❏ September 2012 NRL star Robbie Farah is abused on Twitter after the death of his mother. He later apologises for a threatening tweet he had made earlier to the Prime Minister, Julia Gillard.