Nowadays it is very common the use of the e-mail to delegate duties.
I personally have my doubts that a few lines in an e-mail would clearly define duties, authority and performances better than for example a video-conference or the traditional F2F meeting.
My experience say that once sent an e-mail to delegate a job, and in order to re-establish the control of the situation, and because managers are afraid of making mistakes, they send a second e-mail to ensure subordinates are performing satisfactorily.
Later on, a fear of loss of control arises, and the manager can't resist the temptation of telling the subordinate, in a third e-mail, what, when and how to do.
The latter happens normally once the subordinate has invested a bunch of his time in regard of the subject and its collateral effect is at least a lack of motivation.
