Fantastic article from Wired telling the story of Mark Zuckerberg's notebooking habit, and some of the key facts about early Facebook that have emerged.
Most of these notebooks have since been destroyed as Zuckerberg seeks to claim back his own privacy, but the few tidbits that remain offer some great insights into how his brain works and what he thought was acceptable in building a ~600 million dollar business.
In 2010, it introduced Instant Personalization, a privacy-busting feature that gave more personal information to outside app developers. Time and again, over internal objections, Zuckerberg chose growth and competitive advantage over caution and privacy-consciousness. The result was a series of hasty apologies, not to mention charges and a $5 billion fine from the Federal Trade Commission.