Mark Zuckerberg was leading a meeting in the Aquarium, one of Facebook's conference rooms, so named because it's in the middle of a huge work space and has glass walls on three sides so everybody can see in. Conference rooms are a big deal at Facebook because they're the only places anybody has any privacy at all, even the bare minimum of privacy the Aquarium gets you. Otherwise the space is open plan: no cubicles, no offices, no walls, just a rolling tundra of office furniture. Sheryl Sandberg, Facebook's COO, who used to be Lawrence Summers' chief of staff at the Treasury Department, doesn't have an office. Zuckerberg, Facebook's CEO and co-founder and presiding visionary, doesn't have an office.

The team was going over the launch of Facebook's revamped Messages service, which had happened the day before and gone off without a hitch or rather without more than the usual number of hitches. Zuckerberg kept the meeting on track, pushing briskly through his points