From a linguist's standpoint, there's a fascinating piece on the Atlantic's site about how a school teacher's thoughts on Osama bin Laden's death were merged with a quote of Martin Luther King Jr.'s and have been widely disseminated as MLK's words.
At this point, the "quote" has been repeated millions and tens of millions of times on Facebook and Twitter. Given how many people still misquote lines from movies ... "Play it again, Sam," from Casablana, for instance ... even though the originals are available all over the Internet, DVDs, etc., I expect the entire quote will be attributed to MLK from now until eternity ... sometimes with cross-links to posts like this.
So, for the record, "I will mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy," is the work of Jessica Dovey, a 24-year-old English teacher in Japan.
"Returning hate for hate multiplies hate, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate, only love can do that," is MLK Jr.
Somebody dropped some quotation marks, somebody else Tweeted the wrong bit and the next thing you know, Martin Luther King has new words.