This is something we’ve seen in super-high-end storage systems, but is now being implemented on a enthusiast consumer level. The OCZ Colossus, within its featureless 3.5″ enclosure, sports two RAIDed SSD drives mounted to a single PCB. You can bet it’s going to be fast, though the RAID controller is apparently rated to “only” 260MB/s. With two drives (or four in the Colossus 4X), you’d think they’d easily hit that, but you’d also be right to expect more from a configuration like this.
Price is $299 for 128GB, so it’s still quite a luxury item, but the multiple-non-high-end-drives-in-RAID approach seems to be gaining traction. Of course, for that price, you can get a regular high-end SSD, but if you want to maintain that 260MB/s all the way up to a a terabyte, the Colossus is probably your best bet (though it will be expensive as hell).