One abrupt departure is par for the entrepreneurial course; three, in succession, can start the rumors going. Since I started this beat, I've heard an extraordinary range of baroque tales about Sean Parker. (And people pretend that nobody in Silicon Valley cares to gossip.) Sean Parker is the forgotten man, a founder of Napster, the legendary music piracy site, Plaxo, the online address book backed by Mike Moritz of Sequoia, and Facebook, the social network site; he's been erased from the history of each. Parker, who just turned 27, has a knack for identifying internet sensations, and an unfortunate habit of crashing out of successful startups. He's this generation's bad boy. How bad? Find out later today.