UTSA has just implemented a common-password system for all university online services. In the comment section of this post on Bruce Schneier’s security blog, I learn that these are called Hobbit Rings.
I especially like this comment by Paul Dittrich:
Years ago, a colleague asked “Why do I need to have so many passwords?” Rather than answering directly, I pointed at his keyring and asked him “Why do you need so many different keys? Wouldn’t it be easier to have just one key to open everything?”
He looked at me like I was crazy and said “Well THAT would be dumb!”
(Unfortunately, he did not recognize the analogy between his keys and his passwords.)