What surprises me most about this is that this is a solved problem.
Labels on maps, proximity to their data point, shades to represents importance, placing of labels to ensure clarity... all of this has long been solved in the area of automated report generation, and specifically things like bubble charts.
All that I see when I look at a Google Maps is all of the solutions to the problem of producing legible and clear reports applied to a map.
All that I see when I look at Bing and Yahoo mapping are solutions that have only looked at the domain of mapping and haven't considered whether other domains have solved these problems.
I don't see "tricks" by Google, I just see a set of solutions from one area being applied to the same essential problems in another area.