One of the elements that has evolved dramatically has been the money collection process and focus. This has been honed to an art and science by some, refining the techniques that work best.
A seasoned street performer realizes that, left to their own, many audience members will walk away at the end of a show without making a donation, irrespective of whether of not they understand that this is a means of livelihood - perhaps they believe that somehow this show was otherwise funded or done for fun. So how is the performer to remind them of their duty as patron of the arts?
There are many techniques to collect money from an audience, with varying degrees of aggressiveness and effectiveness. The method of choice for optimum results on acts with dramatic finishes is to hold back the finale and collect before it. Often, the collection becomes part of the act itself, with a variety of comedic solicitations. This can escalate to mass manipulation by some acts. One group I know of routinely spends as long as 25 minutes collecting money before their grand finale.
The tumbling and acrobatic act in the photo is a typical, classic example. The act's finale, where Tylon Moore (Hip Hop Acrobat) performs an incredible forward somersault over seven audience members, is set up with deliberation. Audience members are chosen to stand in a line, lean over, and hold this position while the money collection process begins. There is certainly an element of pressure to donate and guilt for those who do not - this is manipulated to varying degrees, sometimes explicitly.
With other acts, I have witnessed a virtual bidding induced style of collection, where a New York City borough competition is created with announcements being made as to the donation amount and the residence of the donor. Challenges are then made to other borough residents to up the ante. Properly handled, exceptional amounts of money can be generated this way, in something we could perhaps call friendly extortion :)