I didn't realize this before Twitter, but it's a good sign when the response to something you write is angry and incoherent. It means you wrote something novel enough to make people mad, and correct enough that you didn't leave room for actual refutation.

stipulating that this is the case, you still have to have be pretty financially secure to bother risking it - most of us gain nothing and stand to lose a lot from inciting the Twitter mobs

That is an interesting point. What a strange thought: that Twitter could make it one of the duties of the rich to speak inconvenient truths.