I'm quite conventional. I use Dropbox and Drive a lot because I have many shared folders with people that only know one or the other. When in need of having really sensitive information I usually encrypt them in a TrueCrypt container and the upload that to Dropbox/Drive. Recently there was some news about the developers of TrueCryp saying that there are vulnerabilities and disappearing (they were anonymous), but there are no details and there is no perfect alternative yet (some efforts in place to continue development by other people).
I think that is something intrinsic to all cloud platforms, including gmail. I trust none of them, but for not so sensitive information they are enough for me. To Dropbox or Google their reputation is much more valuable than anything I upload.http://storageservers.wordpress.com/2013/09/16/sting-proves-that-dropbox-spies-on-its-user-data/
I heard about dropbox spying and that means no more dropbox for me anymore. Maybe I'm overreacting but that shit should never happened.