A week ago we had an electrical event take out some hardware in our home. I suspect lightning. The list of damage was slight as I have almost everything on a ups. But if a close hit even that won't save everything from lightning. For this discussion I lost a hard drive that was attached to a pogo plug. Thankfully that was a extra backup and scratch drive location. I have time machine backup of my imac to an external USB drive. I also have chronosync running across my network to a 1TB drive. A large amount of my data is on a raid mirror FireWire drive unit. Let's talk about data for a minute. My iMac internal drive is 230GB. My documents, photos and code projects live here. My iTunes library is 310GB which sits on the raid drive. My audio projects folder for all my editing also resides on the raid and is 300GB. Both the iTunes and audio projects get backed up to the 1TB network drive via chronosync. Anyone see a flaw? Yup risk of electrical damage. Had the event taken out more than the one scratch drive I could have lost the bulk of my data. Everything is plugged in and on. That makes it vulnerable. Now I use chronosync to backup my documents folder to my iDisk. My email is all backed up because I use imap with MobileMe and gmail. So those have some offsite protection. The morale is make an offline copy of all your data at regular intervals. Monthly is good. That covers the bulk of your data. Use cloud based storage like MobileMe, dropbox, back blaze etc for your more critical recently changed files. The important thing to check is how amount of your data. Compare it to your backup drives. My iTunes alone is now 310GB. Just enough to fit on a 320GB sata drive I have on the shelf. I recommend as a rule of thumb. Two online backups and one offline at all times. Drive clones, time machine or whatever combination of backup methods suit you.