I use pCloud's desktop app - pCloud Drive - for backup. It's very easy to use because it creates something like a virtual drive that does not take space on your computer. I.e. your files are not duplicated on your computer and on the cloud. You just place the content you need to backup in your pCloud Drive. It's pretty fast compared to anything else I've tested. With most cloud services backup takes ages when you store large content.

I am really sorry to hear that. I have been using Wuala for about a year and I can say it was just fine for my needs. However, I have also been using other cloud services that are highly focused on security, such as pCloud and Tresorit, and I'd like to say, those are very good as well. On one hand, in Tresorit security is the one and only priority, which is very good because I store a lot of sensitive data. On the other hand, pCloud is just as secure as Tresorit, but is a lot more user friendly, and is suitable for regular users as well. Plus, pCloud is more affordable, which, in my view, is an important benefit. So, I personally don't worry about my files right now.