> As your transaction goes into the blockchain, you can be pretty damn sure that won't be reversed, once enough computing power is behind it.
So, this by itself is not an argument. That amount of computing power was produced once, so you can be pretty damn sure that if the incentives line up it will be produced again just on a different history.
I have a few slides detailing the rather scary game theory behind PoW here:
http://vitalik.ca/files/stanford_presentation.pdf
Particularly note the "Low incentive to protect against hacks". If the major Bitcoin mining farms get hacked, raided by men wearing ski masks and black suits, etc in order to double spend, large 51% attacks become possible, and a coordinated global attack could earn >$10-50m via double spends, and even more with shorting at 10x leverage. But from the point of view of each individual mining farm, they only lose at most 10-50 blocks' worth of rewards multiplied by their hashpower - a total private incentive of ~$100,000. In fact, if everyone else gets attacked, it's in your interest to ensure that you get attacked too!
Also, the "bribe attack" variants all theoretically cost under $100,000. In fact, the largest countervailing incentive factor against all of those is the idea that each mining farm has a decently sized percentage of mining power and thus captures a substantial portion of the "public-good" incentive of the network not failing. Now, you can argue that Bitcoin has not succumbed to these and works fine in practice, but (i) right now, Bitcoin is still tiny, and (ii) if that's true, then naive proof of stake, with its supposedly fatal nothing-at-stake problems, will also work fine in practice.
> Nope, bitcoin blockchain forks very rarely. Where is this claim pulled from?
It forks back one block ~1-2% of the time and two blocks ~0.01-0.04% of the time. You can determine this from simple math plus network latency statistics, or check blockchain.info: https://blockchain.info/charts/n-orphaned-blocks?showDataPoi...
This might not seem like much, but if you are looking at the blockchain as an application platform then users are really not used to the idea of finality suddenly becoming non-final 1% of the time.