We spotted this on Gawker.com. From my experience using Google Maps, it rings true (I recently was sent 15 miles out of my way on a trip in rural Ireland).

It seems that Google Maps has plotted the location of a tourist attraction in New Jersey right at the end of a driveway to a private residence. So, on the 4th of July weekend, the owners of the property had to fend off increasingly irate visitors who were looking for the lake and wound up in a private driveway.

So, the data is inaccurate and of poor quality. Google have responded to their error and replotted the location of the tourist area at the lake? Not yet, according to the story on Gawker.