> if the value dropped really hard all of a sudden, for example, it might suddenly be more viable to attack the network In practice, users of bitcoin would sim

> if the value dropped really hard all of a sudden, for example, it might suddenly be more viable to attack the network In practice, users of bitcoin would simply wait a longer time for more block confirmations, namely if you estimated the cost of a double spend attack was $X you would just wait for block confirmations with a total of more than $X of fees + block rewards such that the transaction you are confirming is deep enough in the blockchain to not be economical to include in the double spend attack. Note that the slowness of difficulty adjustments is also a defense here against the further problem of $X decreasing very quickly such that a transaction you had already confirmed becomes viable to attack. Because difficulty changes only every 2016 blocks, if all mining stopped and $X theoretically became 0, in practice you won't get to the next difficulty as no new blocks would be found, so $X in practice wouldn't move.