How much data do you generate per year? I am not including things that you download (music, movies, applications, etc). I'm referring to things you produce yourself... This could be pictures, movies, documents -- anything that if you lost it, it would be gone forever.
Almost a year ago I got an Infrant ReadyNAS NV, and plugged in some drives to create a 800GB Raid 5 network attached storage. Right now I'm up to 9% (around 81 GB). Most of that is taken up by my my photography -- on a good shoot I can easily fill up my 1 GB card. I'm not up to video yet, but I can't imagine that is too much farther away.
Mark Pilgrim had a post a year ago dealing with how you deal with backing up and storing data when today its very easy to generate a half a terabyte a year?
I just recently made an off-site backup with single sided DVDs (all 15 of them), but that really doesn't come close to cutting it when I get up to 50% (probably less than two years away) with pictures or start archiving videos. Soon, the backup answer might be to buy a 300 GB hard drive with an external enclosure, and hard drives become backup medium. I just don't see optical (even Blu-Ray or HD-DVD) making large scale archiving practical. Especially when the shelf life of any medium is in question, true "archiving" is really not a good idea -- how often would you load that DVD with pictures you took five years ago on to your system to see its still good?
I really think the answer is that anything you want to save you need to retain immediately accessible (NAS makes this affordable and still practical) and then make off-site backups (copies) incrementally.
The ReadyNAS has been a very valuable investment (now all I need is a gig-e network to make it truly complete). Down the road, I would probably just buy another one rather than try to upgrade the drives to get more space.