One of the greatest beauties of busking, is that you are able to get a response of some kind from EVERY SINGLE PERSON that knows you are there, and real. Crossing the road in order to pass you with much distance from you, is a reation, a response. Or pretending to get a phone call, or just looking straight ahead or at their watch and hurrying on with an air of importance. It's also a reaction, a response. At this, you can congratulate yourself on NOT being someone like this, at the very least.
The kid dancing, is a wonderful thing, worth more than money at that moment you think about packing up. Kids are a wonderful judge of character, and quality.
A button frequently pressed, on a busker, is the ol' chestnut of watching the busker, tapping your feet, and what's more, so you can take the experience home, whipping out your iphone and capturing 4 min of footage of it, and then cruising off having given nary a brass razoo. Well, it yanks my chain too, but this is always going to happen and the worst thing a busker can do is let it affect her/him.
Many people watching buskers and street performers are tourists. They may not have a grasp of the etiquette that may stand in your neck of the woods, and it's hard to blame them, it's what they know, (or don't)

Humility is in many ways, the very root of busking. Having said that, humility, and busking, and street performing, is not at all for the weak, but rather the very strong.