If you're the kind of person who worries about others editing your work, this recent Google Docs demo will terrify you. In order to highlight the collaboration that can happen in a document, has put up a page that's shared between the user, William Shakespeare, Charles Dickens, Emily Dickinson, and a few more famous authors and poets. If you're slow to write, one of the collaborators will prompt you with a sentence from their own work, and they'll make quick corrections as you type — Edgar Allen Poe is particularly fond of making people "declare" things instead of saying them. Nietzsche, meanwhile, will throw in the odd aphorism, much as we assume he did in life.
It's not a particularly full-featured demo, and we do rather wish you could see the history of your document the way you can in the actual text editor. We also wouldn't mind seeing the authors edit each other, since we imagine at least a few of them would have... artistic disagreements. If you've helped make something you're particularly proud of, you can share it by signing in.
Update: This has been around for a couple of weeks, but our joy at producing words with it will remain untrammeled.