Paul Graham, back in 2008:

The third cause of trolling is incompetence. If you disagree with something, it’s easier to say “you suck” than to figure out and explain exactly what you disagree with. You’re also safe that way from refutation. In this respect trolling is a lot like graffiti. Graffiti happens at the intersection of ambition and incompetence: people want to make their mark on the world, but have no other way to do it than literally making a mark on the world.

Tuesday, 13 December 2011