I agree that if you are a few hundred metres off when arriving at an airfield it is not a problem in VFR as it will be easy to spot. However, with an auto SatNav such as a TomTom you obviously don't get a birds eye view and at a new destination on a dark night with no convenient signposts you can still end up driving around for 10 mins trying to find the right place.
For example, my business partner was invited to a shoot in Cornwall and asked me to set the destination waypoint on his TomTom. I put in the postcode and then checked the position on Google Earth. From this I could see that the SatNav was going to take him 200M to the west of his host's country house which took him up a farm track with a thick wood between him and the destination ..... he wouldn't even have been able to see the property and, by road, he was still a couple of miles from the main gates - totally lost. I created a user waypoint that was spot on the main entrance gates .... the TomTom performed flawlessly and dumped him, at night, on the main drive after miles of country lanes.
I'm sure this will be immensely boring to most pilots, but my purpose was simply to point out the brilliance of Google Earth in pin-pointing waypoints, and then to get the Lat/Long format into one that can be used on a GPS !