When I joined Gmail in 2007 the concept of eliminating deleter's regret changed how I managed all of my data. I went from keeping important things and purging everything else to implementing archive mentality in my whole life. Now I only think twice about keeping huge photo dumps or files larger than about 500MB. Other than that I save everything.
Sure I can predict when I should buy stuff from old sale emails and receipts, but it means that my body of data is important to me as a whole. I'm not trying to personally host the internet or anything, but the data I've accumulated I want. And I back up in a bunch of different places. Once a week I mirror my laptop's hard drive on an external, and I have two other externals that keep old copies or are dead storage for large files. I also use assorted cloud storage that's scattered across a bunch of services based on where I've found free deals for 10 or 20Gb.
It's kind of cobbled together to keep my costs down, but one friend who was scrambling to create a RAID 1 array after a crisis recently reminded me that, "the cost of memory isn't bad relative to the cost of data." So I started thinking about all the different options that are out there and the areas of our data we may be forgetting. What's your system and how has it changed? Do you have any data that you know is exposed, but you're too lazy to deal with? Lock it down below.