I believe they upload a hash of one frame.

Sounds like another reason not to use Chrome.

Isn’t this just more of what caused the problem in the first place? Namely, centralisation. If you store data locally and you lose a machine, that’s bad but not the end of the world. If you store it centrally and you lose the data, that’s catastrophic. Nassim Taleb nailed this stuff. Keep the downside limited, and the upside unlimited or as he says, “Don’t pick up pennies in front of a steamroller.”