When I tell to friends what bitcoin is I always say briefly, it's better to show some videos from youtube or coindesk.

Smb has already posted for example this video.
It's good
https://www.youtube.com/watch?v=Bhe61JaNFLU

Modern marketologists think people spending most time in social networks. And facebook has instrument of targeting... So that's why you and me surely also see it in FB.
But I agree, crypto community is still mostly here on forum. And people like it more. And trust to topics on forum more. 

They have rather big campaign in facebook. I always see their banners everywhere.

Modern marketing says people now prefer more social networks. In my opinion if we talk about very specific field (and crypto is still specific), they should use specific places where these specific people are 
But they already have topic here, isn't it?

Happy New Year, guys!
I hope it ll be nice year for all of us and for crypto community 

Bitcoin very very soon will reach 1000$