I don't know the FB advertising system inside & out either but like Cuban, I'm miffed by this. The implication here is that companies essentially don't own their own "likes." What value do they have outside of being a vanity metric if you can't reach them aside from coughing up thousands of extra dollars?
You nailed it. Lots of great arguments for both sides, but FB owns the platform and all the toys. All big brands know the risks of making big bets to sell stuff in another guy's yard. In a free market FB can move the goalposts all they want,but the reach is still worth the risk until the cost of doing business with them makes the roi equal to or less than other big reach platforms.