I've been working on a blockchain design involving PoS, and it's certainly more difficult to get right, but it's a solvable problem. 51% attacks normally requi

I've been working on a blockchain design involving PoS, and it's certainly more difficult to get right, but it's a solvable problem. 51% attacks normally require 51% stake. It's true that large stakeholders will occasionally have several winning block scores in a row, which lets them create a viable short fork, but it's not really a problem. Short forks just mean that users need to wait for several blocks if they want a high degree of certainty that a transaction is final. 51% attacks could also be more feasible if an attacker can manipulate entropy, but the usual safeguard is to derive entropy from verifier addresses, as NXT does, so that manipulating entropy will cost a verifier their block reward. Then require verifiers to have a certain minimum account age, high enough that grinding attacks become infeasible. Certainly more complex, but with the right design PoS works fine while saving electricity, and the cost savings are passed on to all stakeholders.