Not a lawyer, but: Facebook is not profiting off the YouTube links. They profit primarily off your desire to see what your friends post. A few of your friends

Not a lawyer, but: Facebook is not profiting off the YouTube links. They profit primarily off your desire to see what your friends post. A few of your friends posting YouTube videos is incidental. The subreddit mentioned does seem more like direct profit. Even then I'm sure they could argue their way out of it (they profit off the community, not the 'stuff'), but it's harder. This is why (hopefully competent) courts are necessary to interpret this stuff.