How often do you back up your photos?

[hexensnacht]

Keep copies at secondary locations .. eg. a cheap USB drive at your friends or family's house.
Cloud based systems are ok, but remember that sites like Flickr (advertised above) will be selling access to your images to marketing advertisers and government agencies.
When you upload something to a cloud based system whoever owns that server space can and does actively access your data. If your ok with that, use cloud based systems. If your not, invest in your own solution and update it periodically.
Note : privacy issues for data in cloud based systems is a fact of life these days, it's more that you should be aware and understand it rather then be horrified by it.