Spot the Signs. The most obvious sign that you'll receive this reaction is if you haven't had a healthy relationship with your manager in the past. Maybe you continually challenged his ideas, and he took that as a sign of disrespect. Or, maybe she always made unreasonable demands, and you were never able to see eye_to_eye on your to_do list. Or perhaps his moods were completely unpredictable. In any case, if your relationship has been strained, you may receive a less_than_ideal response to your two weeks' notice.
And sure, this could be an email (all of the same principles would apply), but a letter makes things official in every sense. It also gives you a prop to take along to the face_to_face meeting with your boss, when you let him or her know that you're leaving.