I probably spend too much time following not only our revered Slashdot, but also Kuro5hin and other news/comment sites. In so doing I have noticed quite a few patterns that are common to the 'nerd' and 'geek' oriented sites. I mulled over these a while, then decided just for fun to record my observations and see what shakes loose.
1) The members of site 'B' were frequently former members of site 'A' who became dissatisfied and began their own site.
1a) The members of site 'B' spend much time either openly or subtly denigrating site 'A' and praising how site 'B' is nothing like site 'A'
1b) The reciprocal of (1a) is also true
2) Site 'A' and site 'B' will have nearly the same proportion of trolls and other similar ilk
2a) A number of (fp) or 'First Post' trolls will waste inordinate amounts of time and skill attempting to gain the coveted actual first post. Thus far, I have been unable to determine a causality for this behavior.
2b) One particularly annoying form of troll, the ad-hominem troll, will occur on all sites and strike randomly with crude language and meaningless derogatory comments
2c) Good jokes will become the cannon fodder of the troll
2d) Reading at the default filter levels will not preclude troll posts
3) Each site has a moderation system that some of the site members proclaim better than other sites, others decry as flawed or broken, and the remainder merely ignore
3a) Some of the aforementioned trolls will become experts on this system and its abuses
3b) A portion of the membership will make vain wishes, such as 'I wish I could moderate this up/down/to hell'
4) The signal to noise ratio will never reach above 75% (3:4) due to the aforementioned trolls and the aforementioned membership
4a) The average SNR is less than 30% (3:10)
Under YMMV (Your Mileage May Vary) and other similar and requisite disclaimers, these are my observations. Others are welcome and even encouraged to make your own observations.