So the main point of the article is that China controls > 50% of the mining pool. Is there any reason what-so-ever that multiple companies would ever want to collude and fork it, and thus crashing the value to 0?
Not as long as they own a lot of the coin itself, no. If any of these miners sells their stake, freak out immediately since their next step would be to short bitcoin through some means before causing a value crash. And you’ve also got to consider market reactions; if any of the miners sells a decent amount of their stake, freak out immediately- because they’re liable to sell more soon, causing everyone to freak out and crashing the market. And so on. This doesn’t sound stable- perhaps the whole thing could be taken down by a miner deciding he needs a bit of cash to buy a house.
Clarify? I can’t say the market capitalization of Bitcoin off the top of my head, but neither can I tell whether you think I’m making it out to be higher or lower than it is.
I don't think the issue is a hard fork which would be bad for Chinese miners. It's more about Chinese miners being able to insert transactions. For example, the Chinese government getting all miners to commit to transferring some of the big 'unknown' blocks in the Bitcoin chain into Chinese government control for 'protection'.
That would cause minimal disruption while giving the Chinese government a massive payout. There's a lot of value for China to push that.
EDIT: This would actually cause a hard fork. Any non-Chinese node doing verification would pick up the illegal block and discard it, creating a fork between Chinese and non-Chinese -- with the Chinese fork having the majority of processing power behind it. At that point, you'd just need a Bitcoin client change to exclude the Chinese fork, I'd guess?
I don't think that's possible, is it? My understanding is that the miners decide which of two competing valid transactions is the "real" one, in the case of double spending.
But miners don't have the power to cause an invalid transaction to become valid, if they were to insert an invalid transaction in a block, the block would be rejected by the rest of the network.
That does not matter if there will be a reason. Is there a reason for paypal to ban your account today? Most likely no. But it can. And maybe will. Maybe not. Decentralization prevents that even if they wanted to.