Legal stuff? I have my early years photos stored on DVD as a backup copy. Once I got that 15Mp DSLR, my last 2 vacations were over 20GB of photos, so I now use and external USB hard disk.
Also, I work with software; nowadays, a lot of installs expect you to downlaod the install disk or files and burn your own install CD. The license violation comes if you run the software on too many machines, but having self-made isntall media is not a problem.
I hardly notice the Canadian tax (if it is still there) on blank DVD’s, they are pretty cheap here.
I have about 5 GB of digital photos. Whenever I substantially add to that collection (e.g. after a vacation), I make a new backup DVD of it.
My email inbox and sent folders together are about 1.5 GB. Add in my collection of other data files - Word docs, Excel spreadsheets, CAD files, etc. - and it’s another couple of GB. That collection gets backed up to DVD every couple of months.
My MP3 collection is approaching 35 GB. Instead of DVD’s, I’ve resorted to Blu-Ray discs, which hold about 25GB each. I actually still have most of the CD’s this music was ripped from, but if my MP3 collection were to implode, it would be a lot of work to rip from the CD’s again, so it makes sense to keep a backup.
I keep the latest copies of my backups in a fire-resistant safe at home; I keep older copies in my desk drawer at work, as an “off-site backup” of sorts.
Nowadays my biggest use is installation and recovery disks. Every non-Mac I’ve ever purchased needed me to burn my own recovery disks in case the hard drive crashed. I usually make an extra couple of sets just in case.
I also get a lot of my legal software by download and I like to keep the installers backed up this way. (For example, I got Adobe CS by download to save on shipping, and Intuit now delivers my annual updates as downloads.)
I used to use DVDs extensively for backup of my files, back when 4-5 disks would do it, but that hasn’t been practical for the last few years.