Facebook, It's Simple Right?

This was a recent conversation that I had with my girlfriend’s father, who knows I do web design. Father: I have a business idea. How hard is it to make a Facebook? Me: Oh, that's simple, not hard at all. Girlfriend: No, he doesn’t mean to make a Facebook profile. He means to redo ALL of Facebook. Me: Oh. In that case, that's very hard. Father: Oh, okay. (Pause) What are we talking then, maybe just 3 to 5 hours?