I have data that is important to me (family photos, etc.) on my hard drive. I have a backups of that data running on a Raspberry Pi with an attached drive. If my house gets broken into, or burns down, or hit by a tornado, basically something Really Bad, Backblaze has a copy of my data offsite.

It is tempting to use Backblaze as my only backup, but like they describe on their site, their primary value is as a backup of your backups. Normally you should never have to use them, and if you do, it will be slow. Now if you are in a hurry they offer a service to ship you your data on a thumb drive or hard drive, but that gives you an idea of their primary use.