That's a good point. The presence of the list is only beneficial when people don't know it exists: then everyone acts as if they wouldn't know it existed, so all its doing is preventing those sensitive details to be leaked. However, if you know that the list exists, but you don't know what's on it, you might trust it too quickly... and might only find out that something is NOt on the list if it's too late. So then the existence of the list also contributes towards exposure of private details in some instances, while preventing exposure in many others.