Consistency, is one thing I test for in software. For example, if software refers to something by a particular name, then [usually] it should always refer to it by that name. Furthermore, when it uses that name e.g. 'London Tube Map' I would expect to see such a map, when I click to view it, and not another kind of map e.g.: a street map.
Conventions, These are also an important part of software. People will [usually] expect your software to use conventions that are appropriate for the field. For example, The traditional London Tube map is a schematic diagram, designed to show the relative positions of the stations rather than their geographic location. Though, sometimes it's actually useful to have geographic information, e.g.: is Queensway (Central line) station very close to Bayswater (Circle line)? So if a map isn't using the schematic form, then the geographic form also has it uses.
I would be surprised if I received a London Tube map that was neither schematic or geographic.
Given these two C's, Consistency and Convention, I was puzzled to use Bing Maps...