A thing that drives me nuts is the misattribution of quotations. There is, for example, a piece, sententious and a little sentimental, called 'Success', that the entire world seems to think was written by Ralph Waldo Emerson. The fact that it cannot be found in any of his works you would have thought enough to dissuade people from so attributing it. Quite apart from that, it simply doesn't read like Emerson. In fact it was written by a woman called Bessie Anderson Stanley, in 1904. It was submitted as an entry into a competition, the theme of which was 'What is Success?' She won. The prize money was $250 dollars, with which she paid off the mortgage on her house. So why the misattribution? I think because Emerson has intellectual heft, and therefore lends the piece a certain gravity that it doesn't really have. The other reason is that Ann Landers - the pen name of a Chicago newspaper advice columnist, whose column was syndicated all over America - said that it was by Emerson. Eventually she admitted her error. There are several versions of the piece (it was not written as a poem). Who does the alterations? Who knows? Maybe Ann Landers, maybe Chinese whispers.
Another frequent misattribution is to William Golding on the subject of women. People who don't care for accuracy glue his sentence (taken entirely out of context) "I think women are foolish to pretend they are equal to men, they are far superior and always have been" to the words of a New York 'urban novelist' called Erick S. Gray. Again the intention presumably is to use Nobel prize winner Golding's name to give the quote some kind of weight.
Of course all other quotations, it is well known (excepting Shakespeare), are by Oscar Wilde, Winston Churchill, Mark Twain or Bernard Shaw.