My wife and I both have data it would be quite expensive to recreate on our PCs. Losing it isn't an option.
I subscribed to CrashPlan a year ago after a close call with my DIY backup system using an external USB drive. CrashPlan allows me to back up any PC at this location, and my laptop where ever it is. My wife and I both have PC's with twin 500Gb drives connected as the C: drive in RAID 1. We also have an external USB drive. CrashPlan backs up the PC's to both their central server and to the USB connected drives. The CrashPlan SW is easy to set up (couple of minutes) and so far works perfectly. It is amazingly flexible. I can back up any PC to any other PC here or offsite or to any HD connected to any other PC here or offsite.
The RAID 1 connection covers us for disk failures and prevents related data corruption. I've had 2 disk crashes in 5 years - the second one was what prompted the subscription to CrashPlan. I have a spare drive on the shelf ready to swap out. The disk controller SW takes care of updating the new drive to match the one that didn't fail over night. The USB drive covers us for op system issues or a virus. The off site backup covers us for things like lightening strikes or fires.
Any backup scheme that doesn't automatically store a copy of the data off site is not complete coverage. The off site restore is slow, but it's a lot faster than trying to recreate the data and much more efficient that losing the data.