Rome Sweet Rome, a historical sci-fi saga published as comments at Reddit, was snapped up today by Warner Brothers.
In answer to a question -- "Could I destroy the Roman Empire ... with a U.S. Marine Battalion?" -- author James Erwin posted his reply in the form of a short story. Just a few hundred words long, it was soon expanded with more perfectly formed flash-fics, and the ongoing saga became a hit.
Within days, Erwin--a Jeopardy champion--saw his story receive its own subreddit, where readers created fan-art and fiction to augment his official story updates. There are even mockup movie trailers. According to Variety, WB's Chris Gary encouraged the studio to 'move agressively' to acquire the rights.