[bitfolk] What should I back up?

Hi, I have signed up for the Bitfolk backup service and have to admit I didn't spend too much time thinking what I should back up. I'm interested in a survey of what people choose. Personally I've got: /home/ - because it obviously has files I want there /etc/ - because there are config files in there I don't want to have to recreate /root/ - similar to /home, although I could probably move that /srv/ - this is from when I migrated from a previous provider and I haven't moved it elsewhere. /var/ - I think this is probably the cause of the problem. I initially thought /var/log would be useful and things like that. Do I need all of /var? Probably not. Is there anything obvious I've missed? Do many people just do /? Thanks, Paul