The role of silence in e-mail communication in the early twenty-first century

Have you noticed how silent an e-correspondent suddenly gets when things turn a bit touchy? A suggestion fails to draw a response. A critical comment goes unrebutted. And if that correspondent writes again, the subject of the previous dialogue is not mentioned. E-mail is a good medium for people averse to engagement. Of course, it's also the favorite medium of flamers and nutjobs.