Uninformed people have two negatives to say about paintball. They are wrong, but they say 1) it hurts really bad to get hit with a paintball, and 2) paintball promotes violence. When you meet up with these people, what can you say?
"Try it before you criticize."
A Hit OK, so what does it feel like to get hit with a paintball? It depends. It depends on how fast the ball is traveling, what you are is wearing, if you are making a move. If you're full of that
great adrenaline rush, you might not even feel a hit at all! Ever get popped with a wet towel? Lots of hits feel about like that. Some say it's about like putting a rubber band on your wrist, pulling it out, and popping it onto your skin.
You might not feel a hit if the balls lands on thick clothing or loose clothing. That's why camouflage is great. Cammies are sort of baggy, most of the time. They have thick seams so the clothing lasts longer, and a hit on a seam is harder to feel. A camouflage jacket over a t shirt can give protection from hits and also, by being loose, lets the air circulate. On bare skin, you should feel a hit. It usually stings.
The world gets an interesting color when you take a goggle hit, but you won't feel much. Usually you head a "thwack" as the ball hits the goggle facemask or lens. Not always! Balls that hit the visor, lots of times you don't feel them.
Back to the bare skin thing: if you're really worried about getting hit, cover up that bare skin. Wear a neck protector, gloves, long sleeves, long pants, and a head covering.
Protect those sensitive body areas with padding or hard protection, guys and gals. Do not deliberately shoot at sensitive body areas or bare skin. Avoid head shots, too–a hit to the back of the head can be a thumper.
When might a paintball hit feel "really bad?" A close up hit on bare skin. How do you avoid this? Cover up the bare skin. Another thing to avoid is any close up hit on skin-tight material, so dress accordingly.
Avoid close up hits. Don't get into places where someone has to come get you out with a closeup shot. You have the option to call yourself out any time. If you know you're going to get shot, and you know it will be up close, get out of there. Give it up. It's no big deal and there's another game in a few minutes anyway.
Think about racquetball. Ever been hit by one of them? Think how big a racquetball is. How about getting hit with a baseball? A soccer ball? Football? Tennis ball? Ever been tackled in football, or knocked off your feet going for the ball in soccer game? It's not much to get hit with a paintball.
The speed of a paintball affects how "hard" it hits a target. The worldwide safety standards say to chronograph all markers before play and chrono them regularly during the day. Re-chrono any time a change is made the marker, such as filling the air tank, changing a barrel, changing a part, etc.
The maximum speed limit worldwide is 300 feet per second (fps). Many fields have a lower limit outdoors, such as 285 fps. Ask for a lower speed limit if you're playing in a newbie level game or if the group is all young players. The slower the ball travels, the less energy it has when it hits: less sting potential.
Remember to wear those goggles! Paintball goggle systems are mandatory worldwide. Paintball goggles are specially designed for use in paintball. Do not wear any other kind of goggles (do not wear skigoggles, sunglasses, shop goggles, etc., because these will not protect the eyes from the impact of a paintball).
Standard Paintball Tournament Rule Book: www.actionpursuitgames.com
Safety Standards for Paintball: American Society for Testing and Materials (ASTM)
Paintball Goggle Certification: Protective Eyewear Certification Council (www.protecteyes.org)
Statistics About Paintball: Sporting Good Manufacturers Association (SGMA) 
