I have a terabyte of things that are critical to me. This includes photos, videos and a lot of data for my work. I have an "oh shit!" moment when I was traveling on business and was in between backups. I was out about a week of critical data that ultimately took me > $2000 to get back after failed recoveries.
This is what I do:
1) Schedule a backup to the SAN at my house. This SAN has a terabyte of storage space and is configured to use RAID 1 across two disks.
2) Backup that same backup to my primary laptop, so everything is synchronized from here.
3) Backup that backup to an independent drive that is then placed in my safe (it's a huge safe; no one could pick it up and it can withstand extreme temperatures).
4) Backup the very critical, absolutely-can't-lose data like my family photos to DVDs and store them at my friend's house.
The key is, for me anyway, to have an offsite backup of archive data, because you're not likely to be changing a lot of your photos from years ago. Then you need to have a synchronization of important disks, and for me that's my work.
I tried the online backups but just didn't like them.