If there's a form that requires a user to select, let's say, one of the email addresses he/she has on file in his account, would it be bad practice to make that menu item a drop-down regardless of how many email addresses are registered?
My instinct is to only show the menu item if there's more than 1 option available. This has the benefit of simplifying the form and preventing the user from spending time on a menu item that would essentially have no purpose.
However, couldn't the argument be made that one of the purposes of the drop-down menu (aside from allowing a particular email to be selected) is to imply that the system allows for more than one email address to be registered? Displaying it as a drop-down regardless of the number of accounts registered could help the user realize that more than one email address can be registered while at the same time avoiding the: "What would happen if I had more than one account?" question.
Any additional arguments and opinions to either solutions are welcome.