What are the costs of performing a 51%-attack in
1) PoW?
2) PoS?
Anyone?
1) Hundreds of Millions.
2) Theoretically nothing, if you discount checkpoints. with checkpoints it's hard.
But then there's the social 51% attack where a tiny majority hold a massive percentage of the currency. When this occurs the market is open to extensive manipulation for the benefit of the few, as with real world economics (the 1%).
NXT is a good example of the social 51% attack, the top 33 accounts hold 51% between them. The top 50 accounts hold 61.2%. I'm quite sure the top 1% of accounts (400 ish) hold almost everything, with the other 99% playing with spare change.
sourceI think that's why you see so many NXT shills trying to ram it down everybodies throats on this forum.
In Bitcoin, 2 or 3 guys could gang up and take down Bitcoin or hold it hostage when it gets big enough.. imagine once Bitcoin grew to be US dollar sized and 3 guys could threaten to take down the network(or be hacked or a terrorist organization threatens them by saying they'll kill their kids, or whatever) in Nxt, you'd need 33 accounts to do so? And even then, you'd knock out some of Nxt's cooler features but the main network features could still continue to run even against that attack. And not only that but it is getting better distributed with time, I think the constant downward pressure on the price is proof of that as those with big accounts are continuing to cash out over time.