Bobby encrypted his backup, and he uploaded it to Carbonite. But he couldn't because it was encrypted. He used Mac's FileVault. Leo says that encrypting is a good idea, but after you've uploaded it, it's encrypted, so it's redundant, actually. The thinking is that if you encrypt it, and need one file, you'd have to download the entire backup in order to get it. But Leo says that if you're logged in, then it's unencrypted through the Mac. Carbonite needs an unencrypted backup in order to do incremental backups. And in doing so, they keep your data encrypted on their end.
Here's what Carbonite has to say - https://support.carbonite.com/articles/Personal-Pro-Mac-FileVault-and-Carbonite - "With FileVault enabled, Carbonite does not recognize the files that were already backed up and tries to back them up from scratch because of Apple's encryption process. In addition, using Carbonite to back up a FileVault user directory can cause performance issues. Because of these factors which cannot currently be worked around, it is not recommended to actively use both FileVault and Carbonite."