There has been lots of research about how to automatically produce Goldilocks Maps (enough information - but not too much) - I remember an article (whose URL I can't locate) which showed increased readability by pruning minor location names when they are too close to major locations. Google does that sort of thing well, but they are not the only ones nowadays - for example the osmfr Openstreetmap style does, in my opinion, a decent job of prioritizing labels: http://tile.openstreetmap.fr/