Note that there are potential privacy concerns with Wuala and similar services, as they use de-duplication techniques, meaning if somebody makes a file public, and you have the same copy in storage, they can see these files in your account.
It's not a serious privacy violation, as it only identifies what are otherwise public files anyway - but if you want complete privacy, including being able to hide what you are uploading, not just the content - then you're better with something self-hosted perhaps.
I'd say Wuala, as SpiderOak's mobile application wasn't great last time I checked. It only had read capability.