I'm fifty, I've heard this all my adult life. I'm now retired from one job and work at a bank, quite a few of the older folks that come through say don't give me any fifties, you know they're bad luck. 'Hence the question..
Give them fifties anyway, and an envelope with my name and address on. They can then send their fifties to me and avoid the risk of bad luck. If they actually did this, it would prove conclusively that the saying is true!
Because when you try to use them anywhere, people usually point to a sign that says: 'do the the number of forgeries in circulation we dont accept �50 notes'. you cant get ciggies a beer or anything until saturday morning when you go to the post office or bank !!!