Note that, while SpiderOak is arguably more secure than Dropbox, they rely on a hybrid security model wherein they still have your encryption key on their server, but encrypted with your local password. This matters because if your password is ever compromised, however briefly—say, by using the mobile app or the website, neither of which are supported in a secure manner (they make this very clear)—then all your data would be permanently compromised, with no way to rotate your keys and re-encrypt your data before someone gets access to it, short of blowing out your account. I get why things work this way, but still, yuck.