Just for the skeptics: Yes, trolls exist, in any number of forms. They are so pathetic that it amuses them to start arguments and/or otherwise play with people's minds. The really advanced ones then furiously deny that they are trolling, just to keep the game going. However, the only useful thing to do about them is to treat them as if they were real, and advise them on how to be less inflammatory. If they keep being inflammatory, whether they are lying or telling the truth doesn't matter -- they can't carry on a polite or enlightening conversation and ought to be made to go away.
The people with the ever increasing tragedies are usually something rather different. I know one of these in real life, and while it's not true that all that stuff happens to her, she isn't precisely lying, either. She genuinely doesn't distinguish well between fantasy and reality, as if she were 5, and has an overwheming need for support. Treating it like a small child's story you don't believe it, but you recognize that it expresses an unmet need works best. She is so needy that she has few friends, and they set very clear limits to maintain their sanity, but when she's doing OK she's funny and charming.