To be more precise, when catalogers go bad, it is the worst. Catalogers are a curious subspecies of librarian. They wear cardigan sweaters. They have bifocals. Many of them cringe at the thought of sitting at the reference desk. They see license plates and think they are call numbers or MARC tags. Yet they hold positions of great power in terms of information access. And when they use their vast power for eeeeevil, well ...

One of the very worst public servants in American history started out as a cataloger. I quote from Young J. Edgar : Hoover, the Red Scare, and the Assault on Civil Liberties by Kenneth D. Ackerman (2007):

"After graduating in 1913, he turned down a scholarship from the University of Virginia and enrolled instead at George Washington University, a local school that allowed him to live with his parents while taking law school classes at night. During the day, he took a $30-a-month clerk's job at the Library of Congress, a five-block walk from his house, to earn extra money. He put in grueling twelve-hour workdays with little sleep. At George Washington, he made the extra effort to earn two degrees, Bachelor's and a Master's of Law, before graduating. But it was at the Library of Congress that inspiration struck him. Edgar's job there involved cataloguing [stevenl note: U.S. librarians spell this as "cataloging"] new books, and the library had recently adopted a groundbreaking new system to keep tabs on its bulging collection of over a million volumes plus hundreds of thousands of journals, manuscripts, and newspapers. Similar to the Dewey Decimal System, developed separately about the same time, it assigned each item an index card with a unique code indicating its topic, title, author, and location."

"Sitting at the Library of Congress cataloguing books, Edgar marveled at this new system and the power it gave him to locate any single item instantly in the Library's voluminous stacks. He imagined how, with a few tweaks, he could use it to track anything he liked, even people. He could use it to find anyone, even in a vast country of 105 million souls spanning an entire continent. He could use it to hide things, too, just by manipulating the code. By the time he left the Library, Edgar had so mastered the system and impressed his bosses that they doubled his salary. 'I'm sure he would be the chief librarian if he'd stayed with us,' a co-worker remarked a few years later."

When old catalogers gather around the campfire and swap stories of pure terror, the legend of Hoover usually comes up. The cataloger who crossed over to the Dark Side.