Performers need some limits and restraints, too.

This video of a 1982 U2 concert at Gateshead clearly shows a performer that has completely disregarded his own safety (and possibly the safety of others had he fallen).  The artist climbs the support structure starting around 2:30 in the video.

Were any laws broken here?  Maybe not, as it was the artists' own initiative to do this, however, promoters, venue owners, stage managers, and staging rental companies must be on the alert for this type of unexpected and unplanned behavior so that proper precautions are taken to thwart it or see that it is done with the proper safety protocols in-place.