Backing up is definitely one of those topics that has countless opinions and countless ideas about it. Personally i back up important things (pictures and documents, music for me as well since i dont have that much) between my HTPC and my main pc (which then has it duplicated onto a "backup internal drive" and the original source drive. Pictures we also backup to an external hard drive every so often and those are stored in a safety deposit box.
Theres risk in every method of "backup" so basically its just how important is the data? For me losing all the movies i have on my HTPC just isnt that huge of a deal. Time consuming and lost, yes. But im not going to be angry over it for more than an hour
Music is basically the same way. just means id actually be forced to get rid of crap i dont listen too
. Pictures though....lots of family memories and would be pretty devastating emotionally wise. hence why those we take as much precaution as we can with.
But like anything this is a topic that could go on forever since everyone has different opinions.