Mahajan said that relying on databases and dedicated servers would have restricted the user growth rate, since these resources would have been overwhelmed.
With the online population shifting towards mobile devices, Facebook needs to have a strong presence that they can monetize and control, with unfettered access to the user that cannot be taken away or restricted by another company.
Multi-user support is another new feature for Android 4.2, and while it's restricted to tablet use for now, it's one of our favorite additions to the new firmware.