Discovered that if you use Google Chrome to access Google Maps, then almost all Google Earth features are there. No need for special plug-ins. Quite amazing.
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Perhaps when you install Google Earth, it automtatically installs plug-in. Or, is Flash doing the 3D work??
Note that this works in E9, too, but not Firefox, Opera, Safari. (all latest public version as of 2011-03-15.) To test, just go to http://maps.google.com/, then hover mouse over the Satellite square. If it supports Google Earth, it'll also pop up a “Earth” square.