My thinking is along the lines of UserXYZ posts something humorous and gets 150 points. This causes others who feel they have a funny bone as well to pile in and attempt similarly witty remarks (which are initially harmless or contribute positively); but then you have an avalanche of users who become aspiring comedians on the message boards they frequent. I sometimes feel that these types tend to herd together and give each other a reason to continue with their behaviour by giving one another a few up-votes out of sympathy...
I would also say that the competitive nature of men in general (I'm a dude, and I won't assume anything on behalf of the women here) would contribute to certain sub-groups within this population with an increasing need to out-do one another. Thus a majority of the discussion devolves to one-liners and people trying to be funny, when all they do is come across as cynical while at the same time contributing little value.
In addition, attempts to be funny on a message board are somewhat akin to guessing on questions on your SAT exam: there is no penalty for trying. Whereas weakly setup arguments can carry a penalty of getting a barrage of refutations making yourself look (or perhaps more closer to the truth - FEEL) intellectually weaker.
http://news.ycombinator.com/item?id=119120
I put forth a great deal of skepticism regarding a product and actually got a response from one of the founding members of the company. It turns out that they actually had a real product that shows a great deal of promise...
This just goes to show that sometimes being quick to judge can have drastic consequences for others. I would argue that this is a form of trolling when a great deal of skepticism mixed with anecdotal information from the past (which has nothing to do with the present as things are more mutually exclusive than we would otherwise like to believe) leads to quick karma points and increased skepticism on behalf of other members.
"I for one welcome our new overlords". Oops wait, wrong context. What I meant to say is that being quick to judge is in many ways similar to the reactionary "comedic lashing out" I was citing in the comedic trolling above and can often times lead to making yourself look foolish at no cost to nobody but yourself (as immortalized by Kent Brockman in the above opening sentence of this paragraph!).
Like the comedic attempts above, this is not something that can be easily controlled. Rather this requires restraint exercised on behalf of the author of any given comment. One thing that I feel works against this all is the fact that the anonymity of the internet often affords people to keep doing what they are doing.
The fact that I'm using my real name online (for the first time mind you) is causing me to respond more deeply to this issue and to the open (and unfair) skepticism I was voicing in another thread. Definitely a tougher thing to do...definitely worth it.