In the past I think I've only lost one hard drive due to failure of either the drive or the motherboard. I lost a bunch of pictures and a lot of graphics that I had been working on at the time. I've gotten over it now. I think we all are so used to collecting things that it just makes sense to collect digital files as well. Sometimes it's ok to get rid of some baggage like when you move to a new place and discover how much junk you really have when you are packing.
Yes, I want to keep my computer safe and clean because it's a hassle if it gets messed up. On the other hand, it doesn't really bother me too much to set things up from the start because I've done the process so many times that it's not a big deal. I don't have a lot of personal files that I would categorize as super important. I can write a resume again. Lost photos? Oh well, it's not the end of the world. The file I'd miss most is probably my freaky named, super secretly hidden away file with various website account and password information. I haven't gotten around yet to investigate the best password solution.
Yes, I have a mediocre antivirus running on my Linux and there is no real time scanning but at this point in time, it's not a big threat. And when I get to it I want to centralize my files on the various computers around the house. Maybe then I will have a comprehensive back up plan. Right now, I'd have to attach my USB hard drive to each of my three computers (the iBook is dying and on its way out) and do individual back ups.
I may be a bit complacent because I've never had a personal computer hooked up to the internet running Windows. I practice safe surfing and downloading and the threat to Linux is still minimal. I'm glad to have Windows 7 running on the other half of my new computer so I can learn it and run a few things that I haven't configured yet in Linux, but all the constant security popups annoy me. I'll stick with my Linux 85% of the time and back to a Mac when I have too much spare money again.