I can't be the only person that started scratching my head when it's announced that 10.488TH/s takes up 2 42u racks according to Ken.
Considering ActM has plans to host close to 50TH/s in the same racks within months, I'm not scratching my head at all. Why the hell do you care about hashing density? It's one of the least important factors.
Most important: Time to market/rollout speed
Second most important: Energy Efficiency
Third most important: Energy costs
Fourth most important: Hashing density