I believe that these are nothing more than what I like to call "cheat-shirts". No one who deserves to have that advantage, no one. We do not need to compensate for personal "handicaps" in this game, it is a simulation, one meant to be realistic, not warm and fuzzy, but still fun. When you make it harder for one player to do his job in the game, everyone stops having fun except the guy who you give the advantage to. The only reason I can think of that would make it ok for someone to wear one would be if they had a condition where they can't take impact to the torso, maybe like Mono, were you can mess up your spleen if it gets hit while you have it. And if that's the case, all bouncers should count for that person, or they shouldn't play anyway, cause there's always a risk.
Another alternative would be for chest protectors to have a hard surface, but this raises questions of mobility, comfort, etc. If you think paintballs hurt so much that you need a chest protector, then you are either playing against hot guns, which is the other guys fault, or you should toughen up, or just not play. I play in a t-shirt whenever it's nice weather, and I don't complain if I get hit, cause it's an expected consequence. After all, the other guys objective IS to shoot you...
I recently had to play against someone wearing a chest protector; he looked like he was trying to be a really bad Sir Galahad impersonator. I bounced some off his little getup as he advance up the field, then planted one on the top of his head at 15 yards. He was in much much more pain from being hit in the head than he would have been from taking one in the body, where at least you have some natural cushion of muscle and body fat. So in a way, these things disadvantage you if you are playing against somebody who can shoot.
However, at longer ranges where you would aim for the body to increase your chance of hitting the guy, these are a horrible advantage for the creep who's wearing them.
I think the only fair way that you can play with these would be to agree to count all bouncers, and even then, you have to question the guys honor, and unless you know him well... It would be much better if they were banned from all field, tourney, and any supervised play.
So, in short.....
Take the Pain.
-Captain Clay