obviously there's two sides:

one, it's in public, and isn't there something about "public indecency," "indecent exposure," "public lewdness..." i mean, it's still the law in the u.s.

then there's the other side.... it's a music festival -- it's a place to express yourself, to be free in the moment, and all that woodstock stuff. they're not the first couple to have sex at a music show. (maybe the first to get videotaped though....)

it's just a matter of perspective.