http://www.worldbackupday.com), but I like the idea.
For me the most important data is my family photo and video archive. I do back-up it on my local NAS. And do backup of backup every month.
Once or twice my hard drives crashed, my data - did not.
by the way, if you are not that care about privacy you can consider new amazon cloud storage options . I would say they are cheaper than purchasing NAS or external hard drive. If you want to have reliable backup drive you need to replace it regularly as well, so this is it also not a "once pay" solution.
Anyway, do a backup! And better now!