While Facebook & Google get a marginal benefit from being able to read user-to-user communications, I doubt they're "reliant" on that. They have plenty of other explicitly-public, or intentionally-shared, signals to target their ads. For example, for now the only thing Google is absolutely 'reliant' on is seeing the queries you send their search engine.
Wait, so the standard by which we're deciding whether or not we're cool with unaccountable private entities reading our personal communications for their own (again, unaccountable) ends is whether or not they're "reliant" on it?
It's not that we're cool with it, it's that they don't need it. They can stop if customers decide it's sufficiently important. If all Google had to target ads with was the search terms for an individual search, and they otherwise had no idea who you are or any history on you, they would still be making megabucks. Progressive and All State are still going to pay a ton of money to show ads to anyone who types "car insurance" into the search box.
They might make less money than if they can target more accurately, but not so much less that their business model isn't viable. Which means the issue isn't the business model, it's how to actually design systems that preserve privacy.
People can and do sue Google all the time for violating laws and their own policies for Gmail. Turns out they rarely have a legitimate case, but the point is that Google is not unaccountable except in the imaginations of cynical paranoiacs who, by painting an exceptionally well-behaved company with the same brush as admitted adversaries, undermine incentives for companies to behave well.
No, but the idea advanced by ~fidotron, in the comment to which I was specifically replying, was that big companies like Google and Facebook will fight secure communications because they're dependent on viewing users' communications to make money.
They're not; other more-public or inherently-shared signals are far more important drivers of profit for them. Their businesses leave them plenty of room to be allies in a drive for secure communication.
(Pressure from their governments is of course another matter. But their business models are not a major problem.)
