Newbie: Noun; the oldest known form of internet troublemaker, there have been newbies since the second day anyone went online, or shortly thereafter, when the first person ever online told the second person ever online that he was screwing things up for everyone else. Newbies usually don't mean any harm, but their missteps (POSTING ALL CAPS FOR INSTANCE) are still a real pain.
Troll, also Internet Troll: Noun; a person who posts incendiary comments with the express purpose of provoking an argument. Trolls can turn up in discussions of all sorts; a troll might pick a fight over NASCAR in a stock car racing chatroom ("NASCAR is about as much a sport as cheerleading."), or tout open borders in a Lou Dobbs fan club.
Concern troll: Noun, derived from "internet troll." A more subtle beast than your standard troll, this species posts comments that appear to be sympathetic to the topic being discussed but who, in reality, wishes to sow doubt in the minds of readers. In a 2006 New Hampshire Congressional campaign, a Republican staffer resigned after reports that he had posted to liberal blogs claiming to be a Democrat who thought the party should give up on the race.
Sock puppet: Noun; a writer who uses a pseudonym to add friendly comments to his own blog posts; the sock puppet will rise to the defense of the author, pick fights with those who disagree with the author, and frequently praise the brilliance of the author. The New Republic's television critic, Lee Siegel, was recently found to have created a sock puppet to defend himself from criticism concerning an essay about Jon Stewart. Siegel wrote of himself, "Siegel is brave, brilliant, and wittier than Stewart will ever be. Take that, you bunch of immature, abusive sheep."
Sex bait: Verb; to solicit personal information from others by pretending to be interested in a sexual encounter. In September, Jason Fortuny, a graphic artist outside Seattle, posted a personal ad to the popular online bulletin board "Craigslist." The ad purported to be from a submissive woman seeking a dominant male. Fortuny then posted every single one of the 178 responses, in their entirety, including explicit photos, to a public forum. Many of the responders were easily identified; Fortuny received death threats, voluminous hate male and dozens of prank calls, but broke no known law and has not been sued.
Author avatar: Noun; those who pose as the author of a website or blog post to discredit the real person. This does not quite rise to the level of identity theft the only thing damaged, usually, is an ego but it's remarkably easy to do. Just create a plausible-sounding email address or user name (firstname.lastname@example.org), and start irritating. The most famous victim of this ploy is none other than the perennially grumpy 60 Minutes commentator Andy Rooney, who had his name attached to a well-circulated racist rant.