How many people backup their computer on a regular basis?

Another day spent recovering a customers hard drive which held all their family pictures from the past 10 years. I was wondering how many of you backed up your computer files on a regular basis.

To help me gain a complete idea I would like to know the frequency and methods that you use.

How often do you complete a full backup of your computer files?
i.e. weekly, monthly, rarely

What system do you use to backup your files?
i.e. Operating system backup, online backup, transfer to external disk or flash drive.