The men in the detail turned serious only when we passed through a tunnel. “I hate tunnels,” one growled tensely. “Why?” I asked. “Everything bad happens in tunnels,” he said. “We learned that in Iraq. They can block you in on both sides and do anything they want to you in the middle,” he explained. He only began to relax again when we emerged safely on the tunnel’s other side. “Everything bad happens in tunnels,” I thought, reflecting on the past four years, Facebook’s single-minded race to domination, and every strange, churlish thing that happened that I just had to shake off, because I was trapped in the middle and had to get through to the other side.

I like these security guys, I thought. It seemed healthy to be hanging out with people who had fought in real wars.

The following day, we were sitting at lunch on the roof of the hotel with the skyline of São Paulo stretching as far as we could see when Mark declared imperially, as he gazed at the view, “We’re going to write a book about Facebook together someday.” That sounds fun, I thought, but then my mind reeled with questions. What would that book even be like? The book I would write about Facebook would be so different from the one Mark would write. It was weird that he assumed I thought the same way he did. My face must have betrayed my doubts and questions, because Mark looked at me with his typical coy smirk, and said, more directly than usual, “I don’t know if I trust you.”

You shouldn’t, I thought, giving him a half-innocent look. But Mark’s idea had planted a new one in my head. I could leave to write my own book, I thought. And after so many years of biting my tongue and speaking on behalf of Facebook, it would be a relief to finally speak and write as myself. After all, as The Wire teaches, you should never trust anyone, in business, at least. Keep your hackers close. Mark, who preferred to hire hackers, knew that. And at that moment, I felt almost, for a second, close to him, as if in the mutual ground of breaking into something—him, the business of registering the identities of everyone in the world, me, the company culture he had built—we had finally found a common bond.