Think mosh pit, drummer throws his sticks into the crowd & the resulting ruck makes the Rugby world cup look like tiddlywinks. And this is generally for 10ml bottles of unknown juice. Occasionally a decent vendor will decide that it'd be a good idea to lob atties into this mayhem
Last years expo in Manchester ran to the above but I found being on the fringes (laughing at the idiots scrambling around on their knees) was quite beneficial especially when I'd caught the eye of the american lass whipping up the crowd