RAID 5+1 and BAARF

I am more on the development side, so I have very little experience with hardware. I have read the articles on BAARF. I directly our infrastructure guy to the webpage and he is looking at it. Here is an email I got from him. Is there ever a cause to use RAID 5?

Using RAID1 or RAID10 would increase the cost of the company SAN by atleast a factor of 3.  

I worked on this two years ago, so the information below is 2 years old.  

In SAN (EMC or Hitachi arrays) the issues pointed out by Milsap and others are avoided as follows, keeping the cost low:  

• There are spare disks on the array. The array takes care of automatically replacing a bad disk in the stripe set thus keeping the "reduced performance duration", that to a minimal.
• With lot of cache, fiber backplane and parallel writes to stripes, the "four I/O operations per read/write" issue is mitigated. -- http://www.freelists.org/webpage/oracle-l