TROLL
Trails bait through a likely spot hoping for a bite. The well-constructed troll is a post that induces lots 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. Regularly post, 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 recognizable 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". The irony is the person who makes this accusation is quite often the actual troll.

SPAMMER
What is a spammer?
Someone who continues to post mindlessly irrelevant and inappropriate posts. For example, someone who says, "Stop spamming" is itself spam, since often the post being accused of is not spam at all, but normal discussion.