Zero-knowledge cloud storage considerations

I’m using Wuala’s cloud storage for some years now, and I tried to challenge the status quo to see if there are better alternatives available in the meantime. The main requirement for me is a zero-knowledge provider, a provider that does not know my password and cannot decrypt my data (without brute force). I found these candidates:

Wuala, Tresorit, SpiderOak, MEGA, SeaFile

(Note that SeaFile is a self-hosted open-source solution.) The next requirement is location: Servers should not be located in the USA, and there should be an Android client that supports upload ...

Wuala, Tresorit, SpiderOak^{Double-Plonk!}, MEGA, SeaFile

... and there should be an official Linux client ...

Wuala, Tresorit^Plonk!, MEGA, SeaFile

... and the service shouldn’t require exotic TCP ports such that clients work behind a corporate firewall ...

Wuala, MEGA, SeaFile^Plonk!

... and the service should support file revisions, download on demand only, and files should stay encrypted on client exit ...

Wuala, MEGA^{Triple-Plonk!}

Way to go, Wuala!