Before people become too fixated on that "51%" figure, as they always seem to do, it should be reiterated that's the threshold at which attacks become sustainable for longer periods, but attacks can technically still be carried out with less than 51% of the hashrate. I'd be happy to do away with the name "
51% attack" and simply call it a "
hashrate attack" for the sake of accuracy. It's also worth remembering that an attack is still unlikely, not only because that level of collusion is difficult to orchestrate, but also because of the alignment of incentives. The network was designed to make it more profitable to remain honest than it is to break the rules and cheat.
A mining pool is public though, so other people are possibly mining in BTC.com and Antpool. If that ever happens, people could simply stop, how does Bitmain have the power to make a 51% in that case? I'm missing something?
It's difficult to tell for certain, but yes. It's fair to assume that one single entity doesn't directly control every single last participant in the pool(s). It's largely symbolic in a sense. It puts people at unease when one entity is perceived to have too much influence simply because it doesn't
look good. It doesn't necessarily mean they
have the power to do anything malicious, it just appears as though there's a chance they
might. That's enough to worry some people. After all, decentralisation is one of our most cherished attributes.
Hard fork before too late.
You're free to if you want, just don't expect everyone else to tag along. Seems a touch dramatic for my tastes.