I use a combination of different backups, to try and ensure that if one fails there will always be another to fall back on.
I have the following:
Small external HDD with a complete system image, and always synchronised backup of my documents. This one lives on my desk.
Large external HDD with exactly the same as the first, except it lives at work and only gets updated once a month.
Another Large external drive with backup of photos, which lives at work and only comes home once a month, but, not at the same time as the other.
Crashplan online backup with an online, always in sync, copy of every single document, photo, music file and anything else that is important.
All are encrypted incase someone decided to break into work.
I am properly paranoid of data loss though.