Without developer-signed blocks, Peercoin is easily attacked; with developer-signed blocks, Peercoin is not decentralized.
PoS proponents may next argue that by layering some complexity on top of the basic PoS structure, that they've solved this problem too. Yet they can never seem to rigorously analyze the security of the resulting system.
I was mostly referring to bitshares and DPOS.
Quoting Larimer:
In the case of BitShares, every 101 blocks (17 minutes) represents a rolling checkpoint that has been approved by all delegates. There is never any reason to consider alternative chains more than 17 minutes old. In fact, the client is unable to resolve forks longer than about 4 hours without manual intervention.
Delegates are voted in by majority stake. Some delegates are developers but being a developer is not required to run a delegate node, only gaining enough votes by stakeholders is required. Once every delegate has signed a block, then that block becomes a checkpoint.
For example, the Satoshi white paper convincingly shows that "Bitcoin is secure provided at least 51% of the hashing power is honest." What is the analogous statement for PoS or DPoS? Can that statement be proved?
Bitshares is secure provided 51% of stake is honest.