Yeah I noticed that limit after I put 4 in my shopping cart and then went WTF!
My friend is ready to pull the trigger on a Synology 4-bay and we wanted to load it up with 4 of these for a 9TB RAID5 array. It was going to serve a media/application hub for his new house, as well as remote backups for a few other locations.
The waiting game continues...
+1 btw for a 4TB drive. The 4TB WD RE is just too expensive and I really like the RE drives. I currently only use RE drives in my NAS but the need for greater capacity is outgrowing the need for performance/absolute reliability.