> Dropbox competitors with encryption like Spideroak and Wuala
Unless one doesn't really cares about security and wants encryption for the sake of having encryption, there's no way their implementations could be considered sufficient.
Without audit you're just taking their word for it — which is exactly as when you take Dropbox's word that they won't peek at your data (unencrypted or possibly encrypted but one can't verify that). And to audit those one needs to spend a lot of time reverse engineering their applications, and then auto-update mechanism could render those efforts void at any moment. I've spent about a weekend debugging and looking at decompiled SpiderOak code and while I hadn't found anything suspicious (although I'm not a crypto or security expert) the only judgement I was certain with was "this behemoth's too complex to study in detail, not worth the time to continue the research"
The point is, the data could be encrypted, but it's pointless to just have the encryption — to assume some security one must be certain about many aspects of how it's done — when, how and where encryption keys are generated, when, where and how data's processed, what are exact crypto algorithms used and how they are composed together and so on. And, obviously, a possibility to verify the description completely matches the actual implementation.
So, I think, security should be really done by a separate software module that could be completely reviewed by anyone (from tech-savvy end-users to security researchers) and can't be remotely auto-updated without explicit user consent.