In a certain sense, it would be appropriate to define Facebook a messaging platform. When you post something on your profile, you are telling your friends something new about you.Delay apart, there's no much difference below the information exchange aspect with respect to, for example, Twitter.
Actually, I should clarify. They also all asked "What's an enterprise application?" Now I know that's a technical term in Java but Facebook isn't written in Java. So I think they asked a reasonable question which deserves an answer.
A day job? In an office? My worst nightmare! Comfort me tiny ad!