[yellowstuff]

The argument against negative interest rates was that people could simply store cash in a vault and get a 0% return, rather than lend it for a negative return. In practice very slightly negative rates seem to work out because storing large amounts of cash in a vault is hard. However, it's probably still right to assume that if interest rates are meaningfully negative for a while everyone will switch to storing cash.

[mikhailfranco]

... hence the War on Cash.

They can also convert bank deposits into 'yellowstuff' and put that in a vault, or safe at home. However, the mining inflation rate in 'yellowstuff', plus fees for storage, come to a depreciation of about 1.5%. So if the WoC is successful, and NIRP policies demand less than about -1.5% interest rate, then there has to be a War on Yellowstuff too.