The other backup suggestion's odd too - make a good backup disk passphrase, store it in your password manager. (where's the password manager backed up?)
I was using Wuala but they are closing it down later this year, starting from now. They recommend switching to Tresorit, Swiss based with end to end encryption and no keys held on the server (lose your password at your peril). Any recommendations for cloud storage that is secure and has a Linux GUI? Tresorit is not open source either as far as I can tell from the website.
Nice, doesn't do Windows though which I am locked into at work, and is aimed solely at backups, not sharing and managing files over multiple computers and OSes which is what I was mainly using Wuala for. But you answered the question, so you get an Internet point.
The Deja-Dup front end for duplicity is built in to Ubuntu. It does encryption, and knows how to store in all sorts of places, including locally and on multiple cloud providers.
And, last I checked, SpiderOak's protocol actually has a flaw: they could potentially store a copy of one's initial key. I emailed them about this, but not response.
Cyphertite was really interesting, but it sounds like they're going out of business.