Been looking at their stuff for a while, that blog post got them some really big coverage about 18 months ago and a lot of people seemed interested. If I was going to implement it I'd need to change a few things (like they send data over HTTP which is no good to me, and their RAID pools within each device are centrally managed as they have so many) but the principal of home-rolled storage in that style seems solid.
I actually just got a quote for some of Supermicro's chassis as a base for building one of these, only 16 drives per chassis + SAS expanders though so it's not quite on the same scale. If you look elsewhere on their site they provide links to the company that custom makes their chassis, but I'm not sure if I need the disk density they have so whether it would be worth it.
16x 1TB drives, -2 for RAID6 -2 for hotspares gives me about 10TB-12TB usable, I just need to work out all the costs. :)
It's been posted before quite recently and that blog entry is from September 2009.
There is a group/web forum dedicated to building those and I believe chassis are available from a uk based company.