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).
Yeah, it sounds like the real problem with this is that it will max out the bandwidth of the single SATA II port that it’s connected to. On the other hand, if you had two separate SSDs, each connected to its own port (assuming your MB has on-board RAID, which many do) you’re using two SATA ports, doubling your available bandwidth. This will become less of an issue once SATA III (6Gbps) becomes common.