Actually, thats what they are doing already, to achieve the muti gigabyte drives available today, the controllers function in the same principle as RAID does, by separating the platters. It's not exactly the same technique, but close.
I know this to be true with maxtor drives, as I had an in depth chat with a tech when I had bought my original 30 gig drives and set them up on a raid card, the performance was horrid, with data corruption everywhere, and in looking to find a way to fix the issue, found a very informative tech working at maxtor, who, explained to me that the newer larger mutigig drives use a similar technique, and that the performance was an issue with the firmware of the drives I had themselves, he then authorized a return of both my drives for 2 new ones with an updated firmware. His explaination was fairly simple..."the new technology we use in our drives is fairly similar to a raid 0 stripe, in a 2 platter drive, the controller is split into 2 channels, one for each platter, which allows us to increase the storage capacity, when you connect these drives to a RAID controller card, in effect, you mounting an array on top of an array, and unfortunately, we have seen some compatability issues arise with certain raid controllers. this problem has been fixed with a new drive firmware, again, unfortunately, the only way to have this newer firmware is to RMA your drives" I quoted him to the best of my memory
I said no problem, since getting the new drives ( and I've had them for quite a while now ), I never had a problem.