I don't really expect that anyone would make that kind of guarantee; I'm arguing in the style of a proof by contradiction. These businesses shouldn't be making this kind of claim, and they shouldn't be holding onto data beyond what is necessary. Data should be expunged as soon as possible, because then there isn't anything to protect.

Businesses are acting like there is no risk in holding personal information. When people complain, they respond with claims that the data is safe. When businesses act like they are secured and that we should trust them, we should be asking them to stand behind those claims. I agree, this is crazy, but businesses really want to make strong claims but not be bound by those claims. An honest business that actually believed in their own promises shouldn't have problem putting those promises into a formal guarantee.