Who's Keeping You in Line Online?

That they're solitary folks who shun social interaction is another popular misperception.

"I do interact with quite a few people on a regular basis through chat and e-mail," Keller told ABCNews.com. "It's not like we don't hear another human being's voice."

In fact, moderation companies say that in hiring new recruits, in addition to looking for people with solid backgrounds in communications and online communities, they favor those who are effective team players.

The 'Toxic Poster'

Moderation professionals emphasize that most of the people who use online message boards, and submit user comments, do so with respect for other users and the owners of the sites. But, they say, just one "toxic poster" can derail a conversation and kill the mood for a whole community.

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Sherry Wilcox, 39, a veteran of the industry who works for eModeration from Jacksonville, Fla., said that after more than 15 years in the business, she can predict the direction of the conversation from reading one foul post.

"When you're moderating a site, you know that a discussion is going to go in one direction, and it's not going to be good," she said. "But if you remove that one single post, the whole thing might go back on track."

Although Mzinga's Deirdre said that, on average, she removes 20 to 30 percent of the posts she reads on ABCNews.com, other companies, such as Lithium, said that removing 5 percent of the content on a given site is high for them.

While Web sites differ in their tolerance of unsavory speech, you can be almost certain that the unoriginal perennials -- "scum," "idiot" and "Nazi" -- are near the top of the "do not post" list.

But offensive speech is not a stationary target.

As society's sensitivity to certain words diminishes, those words lose their blacklist status.

Five years ago, Deirdre said, calling someone a terrorist was new to our vernacular. Because it was an unfamiliar insult, moderators would immediately remove posts that contained it.

"But it's like now you can call any Tom, Dick or Harry a terrorist," she said. "So if I unpublish every post where someone called someone a terrorist, it'd be an empty message board."

Moderators say that tensions tend to run higher on political and issue-oriented sites, but they also point out that fires can flare on just about any site.

Jonathan Wishart, 21, a full-time student in Tempe, Ariz., is an avid gamer who followed his passion onto the Internet. Despite his full course load, for 40 hours a week, he monitors a gaming site owned by a Lithium client.

He said that on his site he has seen members duke it out over seemingly innocuous topics, like gaming consoles and choosing teams for sports video games.

"It's a competition. You're trying to show that you know more than others," he said. "It could be two people who are huge fans of Madden. They both love the game, but one person thinks the Cardinals are better and the other, the Patriots. It can be something as simple as that."