I honestly feel like storing all my data on DVDs would be a mite bit crazy. That's over 200 4.8GB DVDs just to store a terabyte of data. That's 7 pounds of pure DVDs, almost a foot high (based on some random website). They just don't have the density for viable large-scale backup. Even at smaller scales, flash drives are more efficient in my book.
If you're serious about backing up all your stuff, the best solution is to have multiple vectors. Personally, I've never had a hard drive fail, but since that is a real threat, a RAID system of some kind coupled with a remote backup of some sort (cloud or another RAIDed machine) should be all you need. The odds of both your local store AND remote store simultaneously dying in a horrible accident are about as high as the odds of a tornado hitting your papers anyway. Unless a massive EMP destroys everyone's electronics, in which case your tax records are no longer terribly important in the grand scheme of things.
Because the zombies are coming.
In the 90's I had hard drives that just outlasted their usefulness, but in the beginning of the 2000's, I had so much hard drive failures that I started questioning how viable hard drives would be, with the failure rate I experienced back then. One of the drives was even subject to a massive class action lawsuit in USA because of its massive failure rate. I was fortunate though... The hard drives started 'clicking', while the whole system stalled as a pre-warning that it was going to die really soon. That enabled me to copy all the data off the drive before I stopped using the defective drive. I also had a drive that died, but if I cooled it down a bit, it lasted long enough that I could start it up for a little while.
Oh, and about SSD's that LennyLen is talking about, one colleague of mine had a drive that stopped working in aeroplanes, and ended up with a nice 'sector 0 not found message', losing all his data. I am not sure if he decided to send the drive for recovery or not, but losing data is a really bad feeling, even if the data is not really that important.
Edit: (Added this here since I discovered that I had the last post anyway, despite GameDev telling me there were new posts here.)
I do get annoyed by people thinking that only storing on the cloud is a backup (e.g., Google's advertising from ChromeOS, saying you don't need to back them up - you do).
That is a bit ironic, since if you ask anyone on the Google Drive team, they will clearly tell you that Google Drive is NOT a backup service. In fact Google won't take any responsibility for any data you lose in the cloud, for whatever reason, stating that it is YOUR responsibility to make sure you have enough redundancy on your data.
If you think about it, it is pretty obvious that you have to take care of your own backup strategy, not rely solely on one single backup strategy.
