The Greater Internet Fuckwad Theory, or GIFT, is the theory of the internet which states that:
Normal person + Anonymity + Audience = Total Fuckwad
First postulated in March of 2004 by popular webcomic Penny Arcade, the GIFT is a concise and powerful statement on the nature of the internet: any person, when given free speech and made invulnerable to any consequences from that power, is liable to be a poopybutt.
Oscar Wilde once famously said, "Man is least himself when he talks in his own person. Give him a mask, and he will tell you the truth." Many people often lie through their teeth and go against their nature to gain a higher social regard, or to at least not attain a poor one. Others, usually the more introverted, will seek to avoid social contact so as to not screw this dynamic up. If you remove the social context of real life, however, their private and unrestrained personalities have a lot less trouble shining through. Add to this the fact that an audience means that whatever you say will be heard, and for many, it becomes compelling to do something show-offish. To wit, the resulting personality is usually that of an asshole.
Penny Arcade cited the general online atmosphere of Unreal Tournament 2004 as 'incontrovertible proof' of the GIFT, but this idea has other real-world manifestations. The infamous imageboard 4chan has very lax standards and a general encouragement of remaining anonymous—most notably on its boards /b/, /v/, and the recent /s4s/—which has led to its reputation as the shady alleyway on the dark side of the internet. And there is a culture of depraved and raunchy discussion on some long-standing trucker CB radio networks that likely stems from a similar lack of rule enforcement and quality control.
A closely related concept is Wheaton's Law, proposed by famous actor and writer Wil Wheaton, which states, "Don't be a dick." Where the GIFT codifies the formula for internet misconduct, Wheaton's Law is an appeal to the humanity in people, to maintain an atmosphere of kindness and respect on the internet (and everywhere else), for the benefit of everyone.