Bitcasa Infinite Drive is relatively new, but it's one of your favorite cloud storage providers in general, mostly because they offer virtually unlimited stroage for syncing and backups. When we say unlimited, we mean it—some of you are using terabytes of storage with Bitcasa. It's not primarily a backup service though, and while it was built for file syncing and storage, the Bitcasa desktop client does support regular file backups. Bitcasa supports Windows and OS X, and encrypts all of your files before uploading so they stay safe from prying eyes. Bitcasa even keeps revision history, so if you've backed up a file multiple times and need an older version, you can pick it out and restore it. Plus, you can use the Bitcasa mobile apps for iOS, Android, and Windows Phone to access your data on the go.
One of the biggest advantages of using an online backup service is that it lets you access your files from anywhere. Most online backup providers let you view and download files from a web browser, but that should be the bare minimum. Many also include file-sharing options, the best of which even let you specify a password for access and an expiration date for the shared item.