A mosh pit is interesting because of the duel nature of the whole affair. The band is blasting music at unbelievable volumes into the crowd, and the pent up anger of a hundred young concert-goers is released in the form of punches, body slams, and various other wrestling moves. But as soon as the hapless soul trips and falls, immediately, a complete reversal of the earlier mood occurs. People who had been trying as hard as possible to inflict pain on those around them stoop and help the fallen gently to their feet and ask them "Hey man, are you OK?"
Walking away from one pit to the restroom, a large man in a "PAIN 4:20" jersey told me, "Man, you're a psycho in there. I love crazy people." He then proceeded to show me the bruise I gave him. Mosh pits may be about releasing anger, but the anger is not directed at the other concert-goers. Instead it is vented into thin air, with anonymous figures taking the brunt. So far it is the only place I have found where you can beat the shit out of someone and become friends because of it.