The middle ground seems to be allowing SARs (which are analogous to tips to police officers), but not requiring banks keep them secret from the customer. The bank could decide to do so, but also could decide not to, like any other speech.
What is the incentive to divulge the information if they don't have to? Customer service? "We're the one bank that will tell you why we are dropping you as a customer"?
Probably some amount of customer service. Banks are at their distrection then on whether they want to tell you or not -- just like for any other reason for dropping you as a customer.
I guess more important than empirically whether banks tell you, it's that it should be their right to tell you if they want.
