After experiencing a hurricane and earthquake on the east coast earlier this year, and being without power for most of the past two days due to the recent snowstorm, I am concerned about how reliable cloud based storage systems really are? Can I really feel secure that my data is safe over the long term while stored “in the cloud�
I'd rather lose my data than trust it to "the cloud". Backup your data to multiple external HDDs (in TrueCrypt containers), and keep them in your gun safe/dog kennel/well/random GPS location/attic/parents' laundry cupboard/empty soup tin/wall cavity etc... Mail a monthly copy on DVD/USB stick to your grandparents/sibling/friend on the other side of the world/country.
Most of the cloud based providers are powered by well-known tech titans like Amazon, Microsoft and Google. Dropbox = Amazon S3 Skydrive = Microsoft I would say it's pretty safe to store data in the cloud.
It depends on what you mean by "safe" and "secure". Would you park your car in the free Google garage, with the key in the ignition?
If you rely on bigger companies for cloud based storage (ie Amazon, Dropbox, etc.) then it's reliable enough.