This happened to me in my own Philly, as my wife and I were going downtown on a date. We were getting off the subway, and a young guy asked if I could break a $50 dollar bill, as they wouldn’t accept it for a subway token and he had to get home. He had it folded up, but it looked real, and I did have change, so I got it out of my wallet. I grabbed the bill and opened it to make sure it was legit, and it was so old and decrepit it fell in half. He wanted compensation as I had just “ripped his 50 in half”. I’m not sure it real or not, but I gave it back to him, and just gave him $3 for a subway token. He still wanted $50 of change for the $50 I “ripped”, but I squared up to him and my sympathetic autonomic system kicked into overdrive, and he eventually scrammed.
I read about this from other people on some local Philly blogs happening to other people as well. I can only imagine what would’ve happened if it were just my wife, so my advice, be VERY selective in who you help out.