Flaming and Trolling

Flaming and trolling are two linked terms that refer to types of behaviour on the Internet, and most notably derive from Usenet and BBS (bulletin board systems) systems. This type of behaviour is still fairly common in IRC (Internet Relay Chat) and at sites such as Slashdot.org.

Flaming

The term 'flaming' is defined slightly differently depending on which site you're on, but generally it means the same thing wherever you go. h2g2 defines it thus:

Flaming means posting something that's angry and mean-spirited - the online equivalent of flying off the handle.
... whereas, according to the Jargon Dictionary, the term 'flaming' originates at MIT1 from the phrase 'flaming asshole'. The definition of 'flame' on this site goes on to define flaming in the following four ways:

To post an email message intended to insult and provoke.

To speak incessantly and/or rabidly on some relatively uninteresting subject or with a patently ridiculous attitude.

Either of senses 1 or 2, directed with hostility at a particular person or people.

(n) An instance of flaming. When a discussion degenerates into useless controversy, one might tell the participants 'Now you're just flaming' or 'Stop all that flamage!' to try to get them to cool down (so to speak).

Interestingly, the Jargon Dictionary also goes on to speculate:

It is possible that the hackish sense of 'flame' is much older than that. The poet Chaucer was also what passed for a wizard hacker in his time; he wrote a treatise on the astrolabe, the most advanced computing device of the day. In Chaucer's Troilus and Cressida, Cressida laments her inability to grasp the proof of a particular mathematical theorem; her uncle Pandarus then observes that it's called 'the fleminge of wrecches'. This phrase seems to have been intended in context as 'that which puts the wretches to flight' but was probably just as ambiguous in Middle English as 'the flaming of wretches' would be today. One suspects that Chaucer would feel right at home on Usenet.
Trolling
For many years, Usenet was the dominant form of online communication. It defined 'trolling' in three ways:

... a posting designed to attract predictable responses or 'flames'; or, the post itself. Derives from the phrase 'trolling for newbies' which in turn comes from mainstream 'trolling', a style of fishing in which one trails bait through a likely spot hoping for a bite. The well-constructed troll is a post that induces lots of newbies and flamers to make themselves look even more clueless than they already do, while subtly conveying to the more savvy and experienced that it is in fact a deliberate troll. If you don't fall for the joke, you get to be in on it.
... an individual who chronically trolls in sense 1; regularly posts specious arguments, flames or personal attacks to a newsgroup, discussion list, or in email for no other purpose than to annoy someone or disrupt a discussion. Trolls are recognisable by the fact that the have no real interest in learning about the topic at hand - they simply want to utter flame-bait. Like the ugly creatures they are named after, they exhibit no redeeming characteristics, and as such, they are recognized as a lower form of life on the net, as in, 'Oh, ignore him, he's just a troll.'
... [Berkeley] Computer lab monitor. A popular campus job for C[omputer] S[tudies] students. Duties include helping newbies and ensuring that lab policies are followed. Probably so-called because it involves lurking in dark, cave-like corners.
Trolling is generally recognised as being an occupation rather than an occurrence, ie while people can (and do) flame for the sake of flaming, flaming can often simply be a manifestation of someone's overreaction to something someone else said. It is for this reason that while flaming is, almost without exception, frowned upon, trolling is more looked upon with scorn than its erstwhile counterpart. The website Slashdot.org, mentioned above, even goes so far as to have a method of forum moderation which allows postings to be classified as 'troll' (as well as such other labels as 'interesting', 'funny', and 'irrelevant'). Users who troll in situations like this generally troll for bait, as mentioned in the definition above.