To answer the most common questions, I am not advocating "build your own youtube."
Instead I advocate what @notTheAuth said below. Basically treat youtube and twitter as my commercials. I don't care who follows me on those two platforms, they are just the entry point. The following that I truly care about is my mailing list and my own personal site. Those are my owned platforms and that is what I care about.
Think of it like the old days of TV. If I am advertising on TV channels and it goes out of business that isn't that bad. Oh shoot I can't advertise on there anymore. It would be worse if my TV show was hosted by that channel because then my TV show isn't there any more.