I'm a database administrator. The best DBAs will tell you that when it comes to data, people only care about what they back up.
When that isn't true, (generally speaking) people who fail to back up important data fail to do that only once. In my profession, it's rare that you get a second chance, of any kind.
Like others have said: no backup/disaster recovery plan is truly useful until you test it, and continue to test it over time. You don't want to be figuring things out for the first time after you've experienced a loss of data.
For those that have "big data", I suggest you either buy or build a machine that does RAID. I use RAID 1 (mirroring), and have for the past 10 years. I've lost 3 drives in that time period, and never lost a single byte of data - nor did I ever have any downtime. I just replace the drive, and ba-da-bing I'm back in business...
My strategy includes backups to external USB-attached drives, which go wherever (somewhere on the other side of the house, or out-of-house, depending). I'm a bit too paranoid about turning over my data to a cloud-based company yet.