Paintball is a very safe sport. Actually, let me make a caveat: paintball is a very safe sport if you wear your mask. There are occasionally other injuries in paintball, but the serious ones are basically always from someone who took off their mask and got hit in the eye (or someone not using a barrel cover when they should). Also, if you properly chrono your gun, then you will even eliminate serious welts. When people follow the rules, paintball is a great, safe way to pass your time.
Why, then do I harp on safety all the time? It's because too many paintball players aren't very interested in it. They have a "it won't happen to me attitude" and they do stupid/illegal things with paintball guns that can end in really bad results. I've been around paintball for quite a while now and I know how much people like to be told, time after time, to be safe. But, since players, as a whole, still break the basic safety rules, it bears repeating, again, and again, and again.