I'm pretty sure most people have self-esteem problems of some kind. Some people have it really bad, though. People in this situation tend to try and show that they're superior to others in some way by denigrating or badgering others. This can be subtle or it can be very overt -- ie. a person with low self-esteem with others might be a complete bitch to others in order to feel a (false) sense of self-importance and worth. One might call this the "bully syndrome", which tends to result in an arrogant prick of a person who has absolutely no reason to be arrogant. The person enters a Catch-22 in which they feel bad about themselves because they have low self-esteem, so they bring others down, so they feel bad about themselves, etc...
A very interesting case study of this phenomena, and a rather recent occurrence I've noticed, is status messages in instant messaging. Many people seem to be using this as a form of unconscious projection of worth. For example, I'm surprised to find people using tactics
such as using the "busy" status when the person is, in reality, just sitting on their ass doing nothing productive. We have this sort of perpetual-busy mode in which the person is so important, so preoccupied, that they simply cannot be bothered by any other lowly worm.
IM is a great vehicle for this type of behavior because of the quasi-anonymous nature of the medium. Of course, whenever mentioning the importance of structure or medium, one is hard-pressed to not make a reference to McLuhan. The medium is the message. In face-to-face conversation, a person cannot camouflage or lie about what they are doing. In IM-land, people use conversational tactics such as status messages in order to not only display a false sense of status, but also to gauge others' reactions based on this. Another trend of note is the "sign-off/sign-in". Since most people have their IM programs configured to (annoyingly!) alert them anytime a person's status changes, this is a clever way to announce to the world that you "have arrived"! It's then possible to gauge who is sitting around on their ass just waiting to talk to you, as a social benchmarking tool. Never before has this been available in social situations. Of course... you have arrived, but you're so incredibly busy that everyone else is just a fruit fly-like annoyance. It projects the false sense that you
-- the person with low self-esteem -- are in control, not the other way around. This type of behavior is why so many people get caught and eventually crumble under their own arrogance.
In the "real world", one greets a person who he knows out of courtesy, and standard conversational rules apply. Online, rules are irrelevant, and the whole concept of conversation
is almost completely eradicated. You can be a dick because -- who cares -- the other person isn't really
there. One faces fewer direct consequences from this. There's no need to say hello in response to a person's greeting because you can fake a facade which you cannot do in face-to-face meetings. There's no need to say goodbye when you're leaving.
We live in a society of declining social interactions and mostly because of growing social ineptitude. People get depressed because they cannot deal with this, try and make themselves feel good by using the "bully syndrome", and eventually receive a type of temporary contentment. The fallacy here is that when something crumbles, your cockiness has left you up shit creek without a paddle.