Credit Suisse will charge rich clients for Swiss franc deposits
Negative deposit rates hit
The notable thing in the SNB decision was a tweake in its basis for interest on deposits. They adjusted the basis for calculating negative interest on sight deposits that are held with the central bank.
The negative interest will continue to be charged on the portion of banks' sight deposits which exceeds a certain exemption threshold. However, the threshold will be updated monthly now to try and reflect developments in banks' balance sheets over time.
That change might have been enough to push Credit Suisse over the edge.
I can't imagine anyone but money launderers being willing to pay for the privilege of holding money in an account.