@mark Today's user interfaces are an excellent example of what @graydon talks about as a prescriptive norm: not only do you have very little choice about what software you use, because oligopoly; not only can they rip out the user interface from underneath you at any time without warning, because you are forced to accept whatever updates the vendor pushes; but also, all of this software is designed by the same small clique of developers who all think the same way and jump on the same bandwagons.