Mark is all smiles until Dave explains the "vomitorium"From a tipster: Omnipresent Facebook evangelist Dave Morin shows up at his company's impromptu toga party to celebrate the social networks' 100 millionth user. To the left, CEO Mark Zuckerberg; on the right, togaless Facebook cofounder Dustin Moskovitz. Can you think of a better caption? Leave your suggestion in the comments; the best one will become the post's new headline. Yesterday's winner: "Bathroom line turns ugly at Gnomedex," by WagCurious.