http://en.wikipedia.org/wiki/Internet_troll#Usefulness_of_trolling
Wikipedia:
The main motive for a user trolling is to disrupt the community in some way. Inflammatory, sarcastic, disruptive or humorous content is posted, meant to draw other users into engaging the troll in a fruitless confrontation.
The greater the reaction from the community the more likely the user is to troll again, as the person develops beliefs that certain actions achieve his/her goal to cause chaos. This gives rise to the often repeated protocol in Internet culture: "Do not feed the trolls".
Houts said:
Now, go back to trolling. And I mean it too. You've posted a dozen times with "Don't feed the troll" being quite hypocritical with your own action.
Just so everyone knows this.
Wikipedia:
Often, a person will post a sincere message about which he is emotionally sensitive. Skillful trolls know that an easy way to upset him is to disingenuously claim that he is a "troll".
Wikipedia:
Examples of Troll behaviour
* Bumping an old discussion, or rehashing a highly controversial past topic, particularly in smaller online communities.
* Intentionally posting an outrageous argument, deliberately constructed around a fundamental but obfuscated flaw or error. Often the poster will become defensive when the argument is refuted, but may instead continue the thread through the use of further flawed arguments; this is referred to as "feeding" the troll.
Motivations for Trolling:
* Anonymous attention-seeking: The troll seeks to dominate the thread by inciting anger, and effectively hijacking the topic at hand.
* Amusement: To some people, the thought of a person getting angry over statements from total strangers is entertaining.
* Wasting others' time: One of the greatest themes in trolling is the idea that a troll can spend one minute of time posting a troll, causing multiple other people to waste several minutes of their time, catalytically affecting others. Most trolls enjoy the idea that they can waste others' time at comparatively little effort on their behalf.
Solutions to Trolling:
* In general, popular wisdom advises users to avoid feeding trolls, and to ignore temptations to respond. Responding to a troll inevitably drives discussion off-topic, to the dismay of bystanders, and supplies the troll with the craved attention. When trollhunters pounce on the trolls, ignorers reply with: "YHBT. YHL. HAND.", or "You have been trolled. You have lost. Have a nice day." However, since trollhunters (like trolls) are often conflict-seekers themselves, the loss usually is not on the part of the trollhunter; rather, the losers are the other forum-users who would have preferred that the conflict does not emerge at all.
