The "Dance, Dance, Dance" thing probably has it's 
roots in the fact that a previous costumer doing
a Bust-A-Move character declined to dance when 
on-stage.  The crowd, which is generally a loud
one, made their opinion clear.

I know that, by far, I'm in the minority, but I 
found the chanting to be disruptive (making a long
masquerade *very* long and having people 
screaming it in my ears gives me a headache)
and (once encourgaged) it put the crowd in a mode 
where they were often rude to cosplayers that 
they didn't find immediately amusing.