Yeah, it's evil. As evils go though, paper darts are mild. I've fought more paper dart battles than most and my eyes, ears, and fingers are all still original equipment. You could do a lot more damage with a hardball or a golf ball than you ever could with a paper dart. The first (and last) time I played paintball, I sustained an injury to my hand far worse than anything that happened to me with blowguns.
I've done things I regret with paper darts. Don't shoot them at folks driving cars with the windows open. They will draw blood from surprising distances, especially if dry. I once put a hole in someone's face from the ground as he stood at a 7th story window thinking he was safe. Always wear some kind of eye protection if you might be in front of a blowgun. Glasses with side protection are a really good idea if you're running around in front of folks shooting at you.
Beware of large angry men. Don't run with scissors. Don't put beans in your nose. If you put someone's eye out, try to be more careful next time. I only provide this information for entertainment.
The real reason that paper darts are Evil has little to do with safety. You will be astonished at how easy it is to litter up a large area with the things. My paper dart career lasted roughly from the age of 14 until I left home for college. My parents pulled the last paper dart from our backyard when I was 35. The paper the darts are made from contains a high proportion of clay and plastic. It degrades very slowly if at all outdoors. Try to pick up after yourself.