Perhaps being an 'important' well-known city counts against being displayed. The more well-known a city is, the less likely you need it to be displayed on the most zoomed-out levels. You know where to click to zoom in if you want to see New York City.
Rather than dismissing Google and Yahoo in favour of Bing, I'd be interested to see if there's any actual user testing in favour one way or the other. Otherwise, it's just uninformed opinion on what 'should' be the best way to use a map.
Because other weighting factors suggested they should be shown.
I wasn't implying a simplistic 'everyone knows where X is, don't show it' system - just that being well known could counter-intuitively reduce the need to show a label at some zoom levels.
Rather than dismissing Google and Yahoo in favour of Bing, I'd be interested to see if there's any actual user testing in favour one way or the other. Otherwise, it's just uninformed opinion on what 'should' be the best way to use a map.