If you are looking for an automatic backup, I recommend Carbonite. It backs up all changed files. The files are available from a web browser so you can retrieve them from anywhere. You would NOT share using Carbonite. That is not its intent. I once lost my hard drive. I restored from Carbonite over the web. It took days to finish the restore. If I ever need to do it again, I will pay to have them ship me a CD or a drive overnight for a faster restore. It would be worth the extra money.
I think the way Office works, your files are stored in the cloud or locally depending on your default. So, if your internet is not available, neither are the files stored there. Carbonite is a pure backup. It works in the background. Depending on how many folders/files you select for backup, Carbonite might take a couple of days to completely back up your existing files.