Any link in the chain will prevent distribution if broken, there is nothing special about Facebook besides being the last - and arguably only - link where breaking a single link is sufficient to break all the chains to the document at once. But you could also prevent distribution by breaking the download for everyone or by breaking the upload for me. As I said, Facebook is only special because it is a singular point, there will always be multiple word processors, browsers, or service providers. On the other hand not even this is really true, if you generalize Facebook to a content sharing platform, then even this singular link vanishes.

So maybe you mean more like the discoverability for people is provided by Facebook. But would this then not also imply that search engines have to filter their search results? And in both cases I could argue that the service provider preventing the upload would also prevent discoverability on Facebook, and not only on Facebook but on the entire internet at once.