51% miners have limited control over blockchain. They can censor blockchain by not allowing some transactions (and forking whenever other miner tries to add those transactons). They can undo some transactions by making a fork before that transaction has happened and eventually forcing the world to switch to their chain.

All those cases are highly visible. I don't know what will happen if someone will attempt to force-fork blockchain. But I highly doubt that 51% miners could monetize that power.

Another point: bitcoin miners are using ASICs, not GPU or CPU. Those ASICs are useless bricks outside of bitcoin mining. If bitcoin miners will collapse bitcoin, they'll lose their ASICs investments. AWS can sell their CPUs to anyone, but mining bitcoin on their CPUs is pointless. To mine bitcoin, you need to buy or build ASICs. And you need bitcoin to stay afloat to return investments from those ASICs.

The only danger is if some actor have lot of money (e.g. US government) and want to kill bitcoin. They can rent some fabs, build lots of ASICs and wreak havoc. They'll spend a lot of money, but probably they'll achieve that goal.

You are almost entirely right, but ASICs can be used to mine other currencies which use the same hashing algorithm.

Bitcoin and a handful of others use SHA256.

Nobody is legally mining on AWS - the margins would put you behind everyone with dedicated hardware, not to mention the lack of ASICs.

That said, if that happened, think about what would happen next: there’d be a mass exodus of customers and breach of contract lawsuits, governments would bring charges under anti-hacking laws, and the rest of the community would agree to rewrite history back to the point before that happened. He’d lose orders of magnitude more money than he could possibly gain, especially given Bitcoin’s limited liquidity.

That last part is key: we have no reason to think Bezos is a crook, or willing to break his customer’s trust, but say he has been completely compromised by Dr. Evil. This still makes no sense because nobody _wants_ a bunch of random hashes — they want to buy things. Even if he could commit the theft of the century, there wouldn’t be any place to spend it with enough volume to make it worth as much as Bezos makes every second.

Exodus of customers? I would bet against that. Flood of contract lawsuits, not likely. Anti-hacking laws used against miners or aws?

You don’t think there’d be a trust issue from showing a willingness to make unauthorized changes to your servers? From breaking their public promises about security, many of which are written into contracts?

Now think carefully about the implications of doing that to steal money. It’s not like they’re hypothetically doing that to hot fix a critical security issue - it’d literally be to profit from betraying their customers’ trust!

I doubt they're getting into mining, their AWS product is in hosted ledgers and things like that: https://aws.amazon.com/blockchain/

AWS does not rent out bitcoin mining rigs and really has no incentive to. To mine at a profit requires expensive, extremely specialized single-purpose hardware that can only be used for bitcoin mining and can't be re-used for anything else.

Not without destroying trust in AWS

Yeah, the idea that Jeff Bezos is going to pull an exit scam on the entire bitcoin ecosystem is ridiculous. He already has all the money.

No.