Just thought I'd add a little to as to why SATA hasn't been taken up by large businesses.
It has to a certain extent but only as cheap storage for either backup solutions or archiving solutions, the main reason for this is reliability.
Hitachi Data Systems in their new SAN's have had to come up with a new RAID standard (RAID 6) to overcome multiple drive losses on single raidsets, as most SATA arrays are made to create large amounts of space you may be raiding 10-20 300gb disks together, this creates a problem in that you have more drives in a single raidset that can fail.
After testing they found raid 5 to be far to unreliable for SATA drives even with hot spares.
RAID 6 allows the failure of up to two drives in any raidset, thus doubling the reliability.
In all the SAN's I've dealth with you have a mixture of drives, SCSI for performance and reliability and SATA for mass storage of none important or archive data. SATA is also used to to take multiple snapshots of the main san data onto for isntant recovery perposes.