To everyone asking about the encryption, it isn't really about protecting your data its about protecting themselves. They have created a service that is billed as a drop box competitor but it's not. This is megaupload2, they just need it to not look like they are marketing it as that.

They needed a way to deny any knolage of file sharing and have found a two pronged attack. The encryption means they can deny any knowledge of what they are serving, and marketing it as a drop box type tool means that they aren't marketing it as a blatant tool for illegal file sharing.