I have to say I am quite serious about losing any bit of my data. It was a time when I backed up everything, including the web-browser history: actually I have dropped this practice only when I realized that every of my tar.gz files overgrew the standard DVD size and that a half of the data I stored didn’t worth it at all.
There is however, a lot of important stuff I’m backing up regularly: projects, documents, Basket notes, emails and so on. A long ago, I have developed a custom automated backup procedure that has been greatly improved with the help of a dedicated server in my home network. The solution is simple, based on standard Linux tools and works perfectly for me.