and how do you tell the difference between someone taking notes on their laptop and someone reading e-mail?
are you also going to ask someone who is reading a book to leave the room? if not, why not? what about someone writing on a pad of paper? now what about someone doodling on the same pad of paper? now what about someone writng the Great American Novel on the same pad of paper? what about someone just sketching a picture?
taking a phone call is one thing, that requires making noise which directly prevents people from hearing you.
arguing that this distracts people around the person is both insulting to those people, and meaningless unless you are going to ban _everything_ that could be distracting.
all other ways of people doing things that aren't paying attention to you should be roughly equivalent. it shouldn't matter if they are using an electronic device or not.
if you have some other hold over the people (like grades in a classroom) you may be able to assert additional control of what they do, but nothing will prevent them from finding ways to do something else (comic books in textbooks is a perfect example of this)