Priceonomics has an interesting article called The Business of Fake Hollywood Money. It’s a really interesting read. I have certainly ran into issues when I have done props in the past – making money realistic enough for use, but in a way that we could do without getting into trouble (its not like you can just go to the local kinkos and plop a $5 bill down on the copy machine…).
The article is also interesting as it discusses some of the Hollywood prop shops. And for listing the book by Fred Reed called Show Me the Money, about the history of money in the movies. It is definitely a book to add to my reading list!