An English professor tries what should have been a fun writing exercise with his class, this is the result:http://themetapicture.com/men-from-mars/
If you have ever seen or tried this kind of writing exercise with anyone before, then you know it almost always ends up a competition in who can produce the most absurd piece of text, with each trying to beat what was written before. (Oh yeah? Well, beat this! Ha!)
I have a couple of friends that decided to write a horror novel this way, on a public forum*, about a teenage serial killer , each taking turns writing a chapter. It was nuts! * unfortunately it doesn't exist any more.