Young couples have long signaled their devotion to each other by various means — the gift of a letterman jacket, or an exchange of class rings or ID bracelets. Best friends share locker combinations.
The digital era has given rise to a more intimate custom. It has become fashionable for young people to express their affection for each other by sharing their passwords to e-mail, Facebook and other accounts. Boyfriends and girlfriends sometimes even create identical passwords, and let each other read their private e-mails and texts.