They are absolutely right with this. You have hundreds of people taking the same pictures - and for what? One of the best shows I ever went to, Jeff Mangum, had a strict no phones policy. They even escorted a couple of people out for violating that. You should be there to enjoy the music and performance, not to take pictures to add to your Facebook collection. The mosh pit is still alive and well at a lot of smaller shows! === Fun fact: Most contracts for music performers at college concerts include clauses barring them from encouraging mosh pits and other similar acts (if they happen they happen, but you can't incite them). They also bar physical contact between the performer and the crowd during the set (IE no surfing onto the crowd allowed). These rules aren't always enforced, but one more thing to keep in mind. Source: I've booked shows at my college and have had the opportunity to read through a couple of contracts.