This sort of thing happens at academic conferences too. Often made worse because the session chairman and the more "prestigious" speakers are old chums and so these speakers get indulged to the detriment of the younger speakers.

At one conference I went to there was a strict 15 minute time limit on the presentations. The organisers got hold of a vintage car bulb horn and used it to call time. After a few early presenters had their talks prematurely ended by a very loud honking noise, the rest of the presenters got the message and the whole thing ran very smoothly over three days.

Come to think of it I have a vague memory that they also had a water pistol that they used on those who thought they could ignore the horn :-)