I actually did this once - just a simple case of tab-whoring and doing things too fast for my own good (it was rm -rf . in my case, in my home directory).
It was a good experience in that ever since that point I've actually been running daily incremental and weekly full backups of everything important to somewhere a normal user has no read/write access. And by 'important', I mean documents etc., not the 500GB of media. It's all about risk vs. cost, and I just don't have anywhere to backup that much data to, when most of it can be reacquired. In fact, I just back up a list of my media instead to make that process easier.
There's a lot of 'ideal solution' stuff being thrown around here, but the fact is that it's not practical for 99.9% of people. Most home user data is not worth the Â£10000 an ideal backup solution would cost.