The plain English meaning of the words "aren't able to access user files" is not the same as "choose not to access user files". Dropbox could just keep keys in

The plain English meaning of the words "aren't able to access user files" is not the same as "choose not to access user files". Dropbox could just keep keys in a store where only automated user accounts can get to them -- ones where only the founders have passwords, or they are in escrow. I think there are ways to restrict the access to founders and a fail-safe, without opening them up to anyone who works at Dropbox.