The End of Money, a new book from Wired contributing editor David Wolman, is ostensibly about the twilight of cash and its replacement with a panoply of more efficient means of exchange. (Think transfers via NFC on smartphones and biometric wallets.) But Wolman is such a thorough reporter of the subject that it's possible to finish his (excellent, highly readable) book and come away with a conclusion opposite his own.
For one thing, Wolman notes, national identity is strongly tied to having a physical currency. That's why, for example, dollar bills are so ugly. The entire point of U.S. dollars, which are common currency the world over, is to inspire trust in the bank that issued them, which is ultimately the U.S. government. Without that magical thinking, they're just paper.
This drive to make dollar bills look consistent across time is so powerful that even though the Federal government in 2008 lost a lawsuit that should force it to create bills in different sizes so that Americans with visual disabilities can tell them apart, it has so far failed to act.