I think there are enough examples of people who've said or written stuff in anger or frustration and regretted it afterwards that I'm inclined to think twice.

I probably wouldn't recommend the anger state to everyone. Just those of us who have found from personal experience that it has its advantages. My default state is carefree and flippant - which results in all sorts of problems if I forget for one second that communications can be taken by rivals and used for their personal advantage. This has resulted in many a regret.

Anger on the other hand provokes goal directed thinking, improved attention and decisiveness when it comes to determining and protecting my interests, whatever they may be.

Unfortunately contempt seems to result in the worst of both worlds. My instincts seem assume that just because someone is blatantly stupid they can't be a viable social threat so I am both flippant and opposed. Big mistake. Contempt is a more useful emotion for people to feel when their contempt producing instincts are finely calibrated to what level of status they can get away with conveying that the object should have in the eyes of the applicable audience.

Judging by the existence of Google Mail Goggles, I'd guess that people often write things tired that they later regret.