We have a huge problem with deer in my neighborhood, but they have never bothered any of my maples -- red, sugar or Japanese. I have heard that they will eat just about anything if they get hungry enough, but I wouldn't worry about your maples unless the deer are very overpopulated in your area with not much else to eat.

Deer ate buds/branches on some areas on some trees for us this past winter and then started in on new leaves this spring. I use hot pepper type sprays to fend them off. They seem to target most of the smaller Japanese maples around here, I have not seen the same damage on my bigger red maples.