A theory introduced to civilization in the form of Socrates, Unwarranted Self-Importance (USI) is the feeling that you are actually worth something despite not having made any contributions to anything at all, thus making yourself look like a complete twat.
This is common amongst LiveJournal and Kuro5hin users, chavs, Coalition soldiers who have actually been to Iraq and others prone to arrogance (Kyle Herman, a wannabe pimp, fits nicely into this catagory and should be slapped for his faggotry). It occurs on ED all the time.
Unwarranted self-importance is also often associated with flamers or n00bs, Americunts, and The French. It will be found on sites where posts or edits are encouraged, as many imagine themselves working for some greater power as they upset others. It also comes into play when the unwarrantably self-important are lacking in one or more areas of their lives, e.g. being too poor to afford a TV. Most people that reward themselves with the feeling that they are important can easily be considered bastards.
People who believe themselves important should seek help, perhaps because of narcissistic tendencies - except for Jacknstock, who was fucking fired instead.