On one of my previous cars I had bullet proof glass. You can either get the armor package, like BMW offers to European models, OR you can get your tint installer to install bullet proof tint. It's only about 200 bucks more than normal tint for your car. The clear tint is thicker than normal color tint, so it scratches MUCH easier when opening and closing the windows. It becomes a pain! The bullet proof tint only prohibits ONE bullet per window from entering the car. FYI. The thickness varies with what calliber you wnat protected against. It's a good idea if you need it, and the weight difference from one color tint to the bullet proof tint is maybe 1 lb. for the whole car - (if that).
Hope this helps the confusion.
BUT yes, for saftey if you ever get into an accident and the rescue ops need to get into your car, uhhh you'll be in trouble. It won't shatter and you could be trapped. A risk, unless you are more likely to get hit in the city. Depending on what lifestyle you run.

 

Thankfully, there's no one out to get me. Atleast I don't think there is...