I've eaten an embarrassing number of paintballs in my life, I don't want to mention numbers but suffice it to say that I've won contests. They taste like crap, have an unpleasant texture, and make your stomach feel the same as it does the morning after a long night of tequila and tacos. That said, they're perfectly safe to eat, at least for humans.
From what I understand paintballs consist of perfectly safe food-grade ingredients as follows:
Anyhow I've been hearing stories, rumors, rants and more lately about how dogs and cats could die if they eat paintballs... Usually it's a handful of balls cast aside unbroken, or broken ones licked off a wall or a tree; no story that I've found mentions a dog sticking his head into a case and munching a whole bag. My fiance, who works with animals for a living, grew very concerned after an article in the local paper - we've got dogs and lots and lots of paintballs.
Now I had a golden retriever who lived to be almost 13, and he ate paintballs whenever he could get his paws on them. He was very well trained, didn't beg at the table, didn't chew things he shouldn't, stayed at your heel and awaited commands, but he went nuts for paintballs. Other than the occasional odd-colored poop I never saw any harmful effects.
Here are some links:
Clearly nothing trustworthy or expert to be found - anybody got solid intel either way?