I've invited several FB people, some that had asked me for directions in getting onto Steemit and others who I think will enjoy what Steemit offers. I'm directing them to your newbies page because you're an ace with engagement.
As far as supporting native file formats for video, right now like you said you can only embed video (youtube, vimeo, etc) on Steemit, not upload those videos natively. If/when they do support hosting video, I'd imagine they'd support a number of formats or at least the most popularly used ones.
thanks for answering the question for the facebook page. I know the user is here in steemit and to add the absurdity of cross-linking, posting, I just posted the link to this page in the Facebook page! Absurd!