Let's face it. There are some very good yet dangerous pitches out there just waiting for you. The truth of the matter is, some buskers have been robbed or worse while trying to entertain and make a living.
Not so much in broad daylight but rather late at night when the criminal(s) may be drunk or drugged comes the danger. Other buskers have also been known to threaten physical violence perceiving you to be on "their" pitch.
Offhand, I can think of 3 places where performing at night is questionable. In no particular order are Amsterdam (junkies), Venice Beach (gangs), and New Orleans (drunk punks).
I remember busking with a buddy in New Orlean's French Quarter. We would notice shady characters working in pairs hanging around watching the hat fill up. But because of the small crowd we usually had around us, they were never successful in ripping us off.
We had to make sure one of us watched the guitars while the other went for refreshments. Somehow, we knew if we turned our backs for more than 20 seconds, we'd find our hat and gear half-way down the block before we blinked.
Another solution if working alone would be to have a fellow busker keep an eye out for such rip-offs while you do your show. You, in turn, can watch his hat and property while he's doing his show.
Using common sense is worth it's weight in gold. If you have a strange feeling about a pitch, skip it and move. It's not worth the aggravation and possible physical injury to perform under these circumstances. Unfortunately, sometimes the busker has to perform or they don't eat that night.
Always plan ahead financially for the worst. Just as there is bound to be rain, you must also take these other factors into account when performing. By using your head, you will live to perform another day...or in this case, another night.