I think its a self-correcting adjustment. When UO/EQ were each hard as shit and the only game in town, they were popular. When WOW came out, it attracted most of those and many new people. Whatever is the easiest/least potentially time consuming model that still incorporates sufficiently intense manifestations of Operant Conditioning and Maslow's Hierarchy will always be the most popular game, I think, and it will just get less involved with each generation of games.

I agree with the previous comments regarding the penchant towards asshat-ness when anonymous. The general real life cultural restrictions regarding acceptable behavior are completely off when it comes to the internet culture. (I wouldnt peg it as MMO or WoW specific, though perhaps it is more prevalent on an MMO where a secondary community is created)

Regarding:

I think this is just general characteristic of Ego and self importance. Have you ever noticed that someone going faster than you on the highway is "crazy" and the people you have to pass because theyre slower than you "need to learn to drive"?

case in point

The stuff you mention, with the exception of crits and other game-specific mechanics, is not at all restricted to WoW or MMOs. It's not even restricted to being online.

It's just the standard vocal minority problem. Unfortunately, WoW tends to exacerbate it due to almost non-existent policing, to the extent that it's probably not even a minority any more. It's also because the game attracts a large number of younger players, and if you've been around a big group of youngsters recently (or are one) you'll notice how their behaviour in real life is pretty much the same as your list.

It's a shame, because if there were even the slightest bit of behaviour policing in the game, we'd see a dramatic reduction in antisocial players. GMs are absolutely not allowed to police anyone for their behaviour if it's within the rules of the game mechanics. That's just wrong - in the "old days" the very job description of GM was policing behaviour. They're basically just tech support instead.

One I really have to pick out in particular, though:
That constantly strikes me too. People who ninja loot. People who disconnect on an instance run because they have something else to do. People who start instance runs knowing full well they can't stay for more than 50 minutes. People who employ, pay or otherwise utilise gold farmer services. People who leech battlegrounds. People who negatively play battlegrounds (HK farm while you lose over and over). People who spent 3 hours hanging around a common lowbie leveling area with a quest mob so they can grief them over and over again (this last point - and I'm not exaggerating 3 hours - was the last straw which made me move to a PvE server).

Most of those people have in fact forgotten that they're playing a game, or have at least forgotten why they're playing it. It's simply a case of "get more gear than your friends". There's a parallel to the Facebook phenomenon - a lot of people use it just to keep in touch, but a lot of other people are only trying to collect as many friends as they can as some sort of social status. It's the same thing. They're playing some other kind of meta-game either against themselves or some other group of people, and they're doing it to the detriment of those that are playing the actual game.

Again, it mimics what those people do in real life, and it's nothing specific to being WoW or an MMO.

edit: I can't believe I missed it.

edit2: I think it is interesting that Warhammer Online for these very reasons is not going to have community forums.

If Blizzard would design behaviour in the game as well, that social world would be utterly dead. The only way to get a social game/site/network to florish, is to let go of most behavourial boundaries.

I'd quit within a second if a GM would interfere with me joking with friends or having sweet and often deserved revenge on the alliance. My behaviour is the embodiment of being me (along with all the imba crits and purple gear, proving my epeen ofc).

Etienne Wenger (a scientist on social learning) would call this the duality between the Designed and the Emergent.

You've just described human nature when given the protection of anonymity. This goes beyond MMO / Gaming / Internet - these things are just vehicles for the bad apples.

Vanguard didn't have community forums.
But it had forums on fansites.
It only made problems worse.

This.

With that said, these forums aren't really the place to philosophize over human nature.