Not quite. Correct on fair use, but not on the transfer of ownership.
Facebook do not get the copyright if you post something which is your intellectual property. You grant them a non-exclusive license to use it. An exclusive license would have the same practical effects of a transfer of copyright, and you would not be able to use it elsewhere, not it's not that. This is true for a lot of the social media platforms, but not all. I'm not actually sure about it on Steemit, it's something I'm looking into actually. My understanding is close to "your material is either public domain or something" 😂 So, in the Facebook, Youtube, etc. case, they can't control distribution (this obviously implies exclusive control), they are just free to distribute it under the terms you agree to.
You certainly can't make sure that anyeon who views (i.e. downloads) your data will not copy it, and it's a big problem. Information wants to be free right? But that's not exactly fair. Again, something else I'm looking into in my recent blog posts.
I'm not sure if it's such a bad deal but it certainly might be and warrants further investigation. The echo chamber is real.