How much of a network do you need to damage before it enters a death spiral?
If you were prepared to dump N% of the PoS network after your attack, what is the maximum N where you're still able to disrupt the network?
Does the same apply to miner attacks?
Truth is, I don't know the answers to these questions. In fact, I don't even have a definitive view as to whether PoS or PoW is the best solution. Most people seem to hold the view that PoW works, but quite a lot of people seem to think PoS won't work. I'm just not convinced about ruling out the possibility of PoS.
ranochigo and a few others on this thread have made some good points. And I agree with them. The more I think about it, the more problems (and merits) I see for both. I just haven't seen a convincing case why PoW is the very much superior to PoS.