Not really. RAID is used for speed. Real backup situations only use RAID if they have some huge file that you can't split up onto multiple harddrives.
You guys are aware that there's more than one type of RAID, right? RAID-0 is for speed. RAID-1 is for redundancy. RAID-5 is for both. You're both right, and you're both wrong.
No. RAID is used for redundancy...that's the entire reason it was developed (hence the name).