I am not sure why, but it seems that many Google Earth users are not aware that you can determine approximate imagery dates in version 4.3. Perhaps the other 4.3 features such as sunlight overshadowed (har har) this feature.
From the user guide: "Google Earth displays the approximate date of displayed imagery in the status bar at the bottom in the 3D viewer. As you mouse over a location, this information depicts the date of the imagery. Note that this date is only approximate."