I feel like there are a lot of parallels between these "private" web services that are extremely dominant, and the "company towns" of previous decades/centuries. Workers didn't have a right to dictate what the town could and couldn't do, and if they were fired or felt they weren't getting enough pay they could always pack up and move to a new town or found their own city with their own money like a good bootstrappy entrepreneur... right?
For some people in the new gig economy of attention/viewfarming, they've found themselves dependent on a particular 'company town' online service. I'm not so much of an anarcho-capitalist that I find this situation hunky-dory.