I have two backup servers; one at home, and one at my office. I back up all the office PCs to both the office and home servers. I also backup my home computers to both the home and office servers.
Short of a giant meteor taking out the city, I figured I'm covered.
I do a full backup every month, and incremental backups each day.
Never had a HD crash (ever), but the backups have helped when for some bonehead reason or another I've managed to F-up a file doing something stupid.
Even won some brownie points with the wife. She had spent several days entering data into Quicken (she balances the checkbook every 6 months whether it needs it or not). Somehow she managed to screw the file up the day after she had spent hours entering new data, but I was able to bring up the backup from the previous day and she was fine.
I think it's much more likely to lose data to human error than hardware failure. Both can and do happen. So back up early and often.