Everyone loves this sort of spontaneous event, but then they go out and vote to eliminate the Arts in public schools.  They'll applaud and soak up the joy and good feelings that such performances inspire, but then quickly forget that artists and musicians need to be taught, and that Arts education has very positive effects beyond simply learning to play an instrument.  

Cultcha isn't spontaneous, although performances of Cultcha can be... 

P.S. When I was an actor, we called this sort of thing Guerilla Theater. I remember an actor friend in the U.K. doing a bit where actors dressed in pajamas would get on a commuter train one or two at a time at various stations along the route and without saying a word, would either sit and fall asleep or stand and read the newspaper.  Then when they got to the end of the line, they all got off and went their separate ways.

You are right. This is very very cool! What beautiful voices, dancing, and such incredible musicians. I've often thought society would be more interesting if we could break out in song when needed. Sure would stop a lot of unpleasantness. Imagine a session of congress.

Just think if someone were at that one mall on their way to apply to work in the shoe store. They would be thinking, "I am so not qualified for this job."