I'm used to going to punk shows with few bouncers, and oh, no cameras. You might have to be a little more cautious, but 90% of the problems you have will be started by the security. At rock shows, most of the time these are crew members and not shy of beating people for minor provocations. Usually bikers or three letter crews, but occationally some minority based "street social clubs".
Next ask, "who is manning the cameras", and expect them to be just as sketchy. Oh the cops? So you trust the police to look for actual theft? Looking for petty theivery is very much on the low list of priorities, and on the top is enforcing strict moral code of looking for an excuse to bust people performing sexual acts or consuming intoxicants. If the music is the slightest bit "counterculture", its any excuse to arrest as many of the party goers as possible, generally making up a reason.
There is never a good reason why you'd want cops at such an event. Unless you expect crews to show up for the show(motorcycle clubs, HC three letter crews, urban corner clubs, etc...), don't hire external security either. Get people who are closer to the music community to resolve disputes.
The other known theif clause sounds too damn close to outlawry, where someone is subjected to being an outlaw and denied rights as a sentance for comitting a crime. This in history has never worked out well.