Dominic recently made a great post on the DFINITY reddit!
However, as you have also pointed out, all things being equal, the state remains vulnerable to malicious systems administrators in data centers. For such reasons, the Internet Computer network will also contain “private computation” subnets, which leverage enclave hardware and other systems to prevent even those with physical access to the node hardware from gaining access to the data. On these subnets, upon which canister computation and storage will consume fractionally more cycles (“gas”), if a node machine is stolen or opened, all that will be found on their storage devices is encrypted bytes.
It touches other points such as 51% attacks, costs and decentralization