>>The number of entities sufficient to disrupt a blockchain is relatively low: four for Bitcoin, two for Ethereum, and less than a dozen for most proof-of-stake networks.
then why we haven't seen a Bitcoin hack before ? Maybe it is the most secured system.
Also the word is "disrupt" so it means some time of chaos, the mining pools never tried to disrupt Bitcoin because they have no incentive to do so.
2. We can go into lower levels and find a number of ISPs specially level 1 ones being able to disrupt the Bitcoin network. Some other single points of failure I can imagine are common routers firmware.
Can Bitcoin never be disrupted? no, does it have mechanisms in place that make it unlikely to be disrupted? yes.
> Even though these Nakamoto coefficients are relatively low, some might argue that exploiting them to attack a blockchain would be prohibitively expensive. While this may be true for individuals, the actors incentivized to perpetrate these attacks include operators of competing currencies and nation-states who have the requisite resources. Perverse incentives can exist with blockchains in the same way that the relative values of fiat currencies can be manipulated.
Nation-states, on the other hand, are the more credible threat. Just because none of them has yet found it a big enough threat to expend the required resources, doesn’t mean it can’t happen.
I feel like the more Bitcoin is used for its original intended purpose rather than merely speculation, the more likely it is to be attacked by such actors.
It's not as if those mentioned entities always have complete control over their mining hardware as those entities include pool miners.
I think there's more that prevents an attack than just being "prohibitively expensive".
My take; people and organizations / exchanges have lost billions. Maybe not on the blockchain itself, but a system is only as strong as its weakest link, and the whole Bitcoin / cryptocurrency system has a lot of weak links and little backups.
I mean if my bank goes bankrupt the money I have in their savings accounts is reimbursed. If my bank card gets stolen to the point where they can withdraw money from it - or if I'm made to withdraw money at gunpoint - I'll get the money back.
https://www.investopedia.com/terms/s/selfish-mining.asp
Because you can make more money keeping it under the radar.