The example of the three locks brings to mind another possible failure of this principle: that it can be exploited by deliberately giving us additional choices. For example, perhaps in this example the cheap lock is perfectly adequate for our needs, but seeing the existence of an expensive lock makes us believe that the regular one is the one that has equal chance of erring in both directions. I believe I read (in LW? or in Marginal Revolution?) that restaurant menus and sales catalogs often include some outrageously priced items to induce customers to buy the second-tier priced items, which look reasonable in comparison, but are the ones where most profit is made. Attempts to shift the Overton Window in politics rely on the same principle.