One of the main reasons of citing original authors is to give credit where credit is due. Here’s another one: If you’re going to use a famous quote in public, make sure that you get it right. Instead of being called out for plagiarism, you’ll be up for public humiliation.
Just ask the vandals in Pittsburgh that decided to deface the Carnegie Library with a quote from what they thought was from J. Alfred Prufrock. In reality, they should have attributed T.S. Eliot and his poem, The Love Song of J. Alfred Prufrock.
I think that Suzanne Thinnes, the library spokesperson, has the best comeback – “They should come into the library and use our services.”
source: Graffiti Vandal Tags Carnegie Library, Gets Quote Wrong, WTAE, Pittsburgh