content: It relies on a consensus among blockchain peers in order to log or validate transactions.  What happens when a single group controls enough of those peers to artificially support a consensus? For the smart contracts, it may rely on data from a server at a specific date and time in order to decide how a deal should be settled, but this means that 3rd party server is now a target (at a specific date and time) to be compromised. So while it all sounds good on paper, it assumes other security issues have been fully resolved and that may never be true for this version of the internet.