The masses were already entertained by AOL chatrooms and ICQ. A lot of older people I see stay in touch with email, and they got each other's addresses by talking on the phone. And they use it exactly like facebook newsfeed, forwarding silly news stories to each other and not being able to format out the endless forwarding chain. They don't think a lick of the innovative engineering and billions of dollars behind facebook, because their batch of friends just forwards emails. I've heard some complaints about the terrible formatting, people asking to be taken off the lists, people not knowing how to do it, but it mostly works. Facebook confuses them too. Some only use Skype.
What is facebook when you boil it down to its real functionality?
Address book with photos
Event system for the address book
Mail forwarding between people in the address book
Filters for forwarded messages
Filters for people in the address book
Media storage and filters on who can view it
But mostly a UI that enables a larger percentage of casual computer users to use more of these features than they could in email. Takes the friction out of the forwarding messages use case. Sharing photos and the address book are in one place and searchable.
A single UI for a bunch of features that used to be a mess of separate UIs http://static3.businessinsider.com/image/4dd4d1cf4bd7c8c90f0...
And there are your entertained masses and billions of dollars. But what was it worth when half of those features were stuck in email?
The GUI and the way we organize programs is why we shoveled a bunch of these features from one place to another and made a big fuss about it when an unknown proportion of users started using more features than they did in email.