>You receive updates to the blockchain in a PoS world. This is literally no cost to someone trying to commit fraud against you by staking their coins and creating fraudulent blocks.

Ethereum proposes to prevent this by including "slashing conditions" that inflict large penalties on the type of fraudster you're talking about [0].

[0] - https://github.com/ethereum/wiki/wiki/Proof-of-Stake-FAQ#tha...