Conditionally yes.
I definitely share your skepticism! As long as you store them in strongly encrypted files (and I don't mean a password protected spreadsheet), then I feel safe storing the information on the cloud. Most of the agreements I have seen regarding free cloud storage allow the provider to scan the files. (Nothing is ever truly free).
Of course securing the documents may preclude you from gaining access easily, especially from a tablet or phone. But there are options, for passwords KeePass has an app I use for storing passwords. There are some apps that allow you to use TrueCrypt or other strong encryption to access and save encrypted containers. That could work as long as the containers are small enough for quick access from mobile devices over relatively slow links.
There is NO WAY I would store un-encrypted or weakly encrypted information on the cloud, regardless of the provider.
