Like JacFSB I have no taste for this. In my mind, it's only a little weaker than the dormant account fee; i.e. it relates more to a "fee opportunity" than charging for a customer action or inaction that actually has an effect on the bank.
I've always been big on attempting to locate customers immediately after our communications have been interrupted. If you can produce a laundry list of things you actually do to reestablish contact and they represent a direct expense, then I could be persuaded that a one time fee is justified. If your bank just plans to take a few bucks out of the account just because no one is watching, then, No.
As for checking and savings account customers where you have a legal responsibility to provide periodic statements, from my perspective it's a fee "in connection with the account" and disclosure would be required. I'm uncertain as to how you are inconvenienced when I have a time deposit and I get lost. Same for a loan.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.