Think you nailed it - the most important problem is overcoming the social friction that enables companies to centralize control of entire industries for no reason other than - they got to it first. We need ways for consumers to organize en-masse to switch services - since trickling out one by one has such a disadvantage ("all my friends use X...").

My hope there, if any, lies in someone developing a mature incentivization system to get people to commit to leaving en-masse. If you just have to click a single button that says "I'll leave Facebook if 50% of my friends do", then that's super low effort - and as soon as those commitments trickle up to a big enough number, the software can organize the move en-masse. Problem is, nobody needs to actually commit to that, so there might need to be additional layers of carrot/sticks.. but that's doable too! You could e.g. commit $20 to your decision, and the software could automatically track whether you followed through (e.g. leaving Facebook for Freebook). Likewise, many of these migrations ("mutinies"?) could be very lucrative for the receiving party - so much so that they might be happy to pay people that $20 to move, just to guarantee future business. (and presumably Freebook would be a little less evil than Facebook). The problem today is just that anyone who hates these services has to make so much effort to do anything useful about it that it's just never going to happen. We require mass-organization tools. (These are also, coincidentally, the exact same tools needed for effective Unionization, so - speculate however you want on why they don't exist yet).

Additional comment, for what it's worth: the underlying system of contracts that implements the above is a very strong use case for blockchain technology and cryptocurrencies. The amount of power and flexibility you get at dealing with all the complex financial incentives of the above could really come in handy - especially when you consider that such organizations will probably also need some kind of internet governance to decide what to do (which decentralized software is key for). With crypto, it's forseeable you could even do some crazy things like tie the incentives for each user to a (e.g. Facebook) stock-shorting contract - effectively making a profit off of tearing down one company and moving to the next... self-financing the whole movement.

And that to me then begs a whole other realm of speculation, because if this kind of organizational technology became widespread and actually used by people - shit... the entire relationship of consumer and producer gets flipped over. Any company that's making profit, unless it has some completely unique quality that can't be repeated by another startup company, could just be attacked by this mob of consumers - transferring all business to the new company en-masse, giving them even less profit. I guess in theory that's kinda how it works already, but this really could up the carnage to levels we've never seen before - and takes away that inherent platform advantage that so many companies are leaning on.

In summary though: yeah, seems the biggest problem is platform centralization. Moving from that requires high-quality decentralized platforms, and organizational tools that can incentivize and plan such big en-masse movements. I believe the tech to do that is fresh, still being worked on, but is coming - and it could have some pretty cool implications for how the world works if it does.