When I worked at a large company, their reason for storing passwords (to an online ordering system; for some 1.5 million clients) as plain text was the ability to impersonate users when debugging their problems. Then, after a while, even that became too hard for them so they added a special backdoor: on the live system, you could go to a special page (it was not linked from anywhere, but it was conveniently named Login.aspx) and enter the user ID and a shared password that worked for all users. I'm still amazed why this had never been taken advantage of while I was there.