It's interesting. If they wanted to, they could compete with the likes of HP, Dell, Lenovo, and Cisco if they could ramp up production to accommodate customers. I wonder who does their manufacturing on the backend.
Facebook uses Quanta/QCT, Celestica, and Accton for a lot of their manufacturing. You can buy Facebook servers from companies like Hyve, AMAX, and Stack Velocity but they aren't really aiming at the mainstream server market.