If it needs cooling, manufacture would put it on.. but most of those high-end HD, scsi, are in a server which sits in a ACed room, so they assume it'll be cool..
I have several drive, regular 7200 ide and they seem to get pretty hot... I just have one of those flat cooler on it and it seems to cool fairly well.. from hot to warm... but guess what... most of them still failed... RMA a bunch of drives that were on cooler... it's good in theory but drive still fail... I guess anything mechanical fails after a while...