The main problem, as I see it is that type, as a communication medium is a very flat and restricted one. No body language or voice inflections are there so people can judge intent of words. Those with a clipped curt way of speaking, and translating that to type can come across as aggressive where maybe it is not meant to. Others may post more words in an effort to try and get around this type problem.
Apart from obvious times when people are not getting on, I feel that the typed medium is the real culprit along with how a person is actually feeling in themselves on the day which may or may not distort their perception of words, on both sides.