Since Mat Honan's worst-day, I've seen several posts about backups. Shawn Blanc wrote a nice summary of his system. I think he is 2/3 to a good system.1 I'll offer up the advice I give to anyone that will listen.
Online backups are nice, but nothing beats an offsite physical backup.
I've written about my backup OCD before and not much has changed.
I've tried all of the major online backup services. All had some amount of impact on system performance. Most required a great deal of time to backup. Maybe it's because I'm a natural skeptic or maybe it's because I've only met one person that ever restored from an online backup, but I have serious doubts about the value of these services in an emergency.
I use Arq to backup encrypted disk images of my most personal data. It's encrypted because I don't trust people. It's a disk image because I don't trust software. A DMG file can be mounted by any version of OS X. I can also browse to Amazon S3 in a variety of ways to get to the file. It's not a black-box user experience.
Physical Offsite is the Canonical
I keep two offsite backups. There is one hidden in my home. If I am robbed, I can reclaim much of my past digital life within minutes of getting a new Mac. Music files can be repurchased, but baby pictures can not.
I also keep another physical backup at work. If my house burned down, it would only take me a couple of hours (and a new Mac) to get back to a recent state.
These backups are not real-time but they are close enough. 30 days old is still better than nothing. If you want my advice, clone your data to a hard drive. Send it to someone you trust to hold it. Repeat as often as you both can tolerate.
To be fair, Shawn never says that this list is his complete system. ↩