I might kick this question over to some of the blind American people on my friends list, but, first, a good number of the blind people I know CAN, with pain and difficulty, squint at the corner of a bill almost enough to get a vague idea of what kind of bill it might be.

And, other than that, blind Americans are taught to fold each of the denominations of bills in their billfold differently, to distinguish between them.

So, what's to stop someone from giving a blind person a $1 bill in change when they should get a $20? Um.

The fact that ripping off a blind person that way is SO low that even scuzzballs can sometimes feel bad about doing it?

Yeah. The system could be improved.