In a lot of environments.
Peter gives a nice overview why you don't always need to invest in big fat redundant hardware.
We've tackled the topic last year already ..
Now I often get weird looks when I dare to mention that Raid is obsolete ..people fail to hear the "in a lot of environments"
Obviously the catch is in the second part, you won't be doing this for your small shop around the corner with just one machine. You'll only be doing this in an environment where you can work with a redundant array of inexpensive disks. Not with a server that has to sit in a remote and isolated location.
Next to that there are situations where you will be using raid, but not for redundancy, but for disk throughput.