Hi,
Following scenario: A government would like to destroy Bitcoin. It buys a significant number of ASICs to build up a huge mining farm and carries out a 51% attack.
From my point of view it will not be so easy to buy so many ASICs as once - what do you think?
Absolutely, that's usually the first argument I make when discussing 51%. Is there enough hashrate available so that it surpasses all the hashrate allocated to Bitcoin ? If so, why not mine Bitcoin ?
Even if it's for trying to hurt, a one (or two?) block(s) reorg won't affect the network that much (if not at all, for one block). Trying to reorg >2 block becomes really difficult..
Another question: Will it be noticed (how?) that somebody buys a big stack of ASICs and/or are we able to identify such a behavior monitoring the network's hashrate?
If the aim is to 51%, then the hashrate won't be allocated to the Bitcoin network. So, no, not by monitoring the hashrate.