In an era when a growing number of young people have no idea how to write in cursive, using a signature as proof of identity feels especially passé. Historically, credit cards have not been considered valid for use unless a customer has signed the back. In reality, most cashiers these days overlook the "Not valid without an Authorized Signature" warning (if they even look for your scrawl), but before technological advancements made handwriting a thin line of defense, banks used them to ensure shoppers' identity