Mark's guidelines on good etiquette for communication are commonsense. Email tends to encourage swift replies made with insufficient thought. It is true that lack of news can be as frightening as a crypt, and some of the skeletons may want to whistle or rattle their bones to keep their spirits up.
On the other hand, there are plenty of lively mailing lists and blogs which maintain a high signal to noise ratio and generally contain interesting, useful and courteous material. I do not think the medium is to be blamed.