Funnily enough, last week when I was on holiday at a UK Chav training camp, sorry...Haven camp site - (mind you they both have HAV in the title

), the lifeguards around the pool weren't allowing either still photos or video to be taken around the pool area.
Theres obviously the invasion of privacy issues, together with problems of what some unsavoury types might do with such footage, especially (unfortunately) of children innocently playing.
A sad sign of the times.
But, from the point of view of this topic, if you're going to take photos or video footage at a disco, I guess that it would be wise to ask for permission - perhaps in a Readers Digest Tick Box type way...
EG: "I'm planning on taking a couple of photo's during the night, if anyones got any objections, please let me know before 9pm - thanks folks".