If I ever go completely storage nuts I think I will build a rig taking a page from BackBlaze's book.
http://blog.backblaze.com/2011/07/20...-more-secrets/ 135TB in a 4u server chassis.
I wouldn't go for the full 135, I would be more than happy with 24 or 32TB. A few weeks ago I actually came across one of these in a data center.
BTW that pic is one I just grabbed from their blog for illustration.