The blockchain can be tampered with if the crook has the cooperation of 51% of the hash rate.
Last night Sye posted to Facebook that just one very wealthy Chinese lady contributes 20% of the hash rate.
I emailed that wonderful news to a friend who soon after replied that just five people control half the hash rate.
Electricity is real cheap in China because the Commies think it's cool to die of asthma.
One can "bootstrap" a mining operation, by spending all of one's mining profits to buy new mining rigs.
To some extent that's required of every miner because the coins become more difficult to mint each time a new coin is minted.
For example, Satoshi's original paper demonstrated that there is a hard limit of 21,000,000 bitcoins that can ever be minted. Since 2009 or so 16,000,000 have been created but that hard limit is not expected to be reached until a century from now.
I was wavering over whether to by an Antminer S9. With the required APW++ power supply the S9 costs $1555 - payable in BitCoin Cash. :-/
It's not the cost that was troubling me, but my concern that I won't tolerate the fan noise. My new rig is going to consume 1350 watts so I can turn off my apartment heater, but without those to turbojet fans the S9 would melt into a puddle of molten aluminum.
What clinched my decision to buy one anyway was Sye's Facebook post that said that just one very wealthy Chinese lady owns 20% of the world's hash rate.
What sealed the deal was my friend telling me that just five people control 50% of the hash rate!
Doing My Part For The Dark Net,
Michael David Crawford