What might explain online incivility?

Here are some possible explanations for why there is a lack of civility online:

• Lack of manners guidelines

* there are many guidelines for kids and educators/parents to teach how to be good digital citizens 

* Commonsensemedia.org is one excellent resource: http://www.commonsensemedia.org/educators/blog

• Online disinhibition effect - Like being in a crowd, online behavior can allow people to feel less inhibited in what they say online.

* avoid the disapproving looks
* lack of hierarchy or status differential
* absence of non-verbal cues to intent and meaning
* de-personalization with anonymous, automated communication

• Wild West mentality: little or hidden enforcement of social norms, so people act in ways that make them feel like they can say anything they want without fear of retribution or laws.

• Sensory overload - can't figure out which media is appropriate to comment because so many media are open and viewed.

• Sleep deprivation - we know what lack of sleep can do for judgement 

Can you think of others, or expand on these?  Do you agree that these might be some reasons?  Why or why not?  Clive "the jive" Bundy made it to the front page of the NYTimes today.  I think his mentality, and those of his "cowboys" has an air of Wild West lawlessness about it (and they have the horses and hats to prove it).  But they think they are just being patriotic - and going against the government is about as patriotic as you can get, if you're a tea party advocate.  

Are there other examples that you chose that fit these explanations, or do you have other reasons?