Right after minute 32:00 Alex Schultz says "Facebook was viral via word of mouth because of the awesome product". Is this really true? I think "Use your email login and password and invite your contacts" namely contact import was the viral technique. The payload and frequency was high and the CR was ok.

I remember Facebook growth days somewhat well. People logged in with their emails and passwords were asked to provide their email provider passwords (to be fair, somewhat deceivingly) to invite everyone in their addressbook to come to Facebook. And I remember quite well some people didn't event notice the difference between whether they were asked for a Facebook password or their email provider password, and didn't really understand what was asked by inviting their friends.