The problem with RAID is that most data loss doesn't come from drive failures, but from either malware or finger trouble in meatspace.
Not much use having 4 ex-copies of your irretrievably deleted file on you RAID array....
RAID has it's uses for a server, but is not a substitute for secure backups in a SOHO setup. I'll stick to offsite backups and onsite regular mirror backups in grandfather/father/son style.
