Roger Long recently wrote an article about a ledge in Whitehead passage (Maine's Casco Bay) that appears on paper charts, but is missing from many vector charts used in gps chart plotters. You can find it in the 2010 mid-winter issue of Point's East Magazine
, (p. 26) which you can access from Points East archive.
The location is shown below in this snippet from NOAA 13290 using their online chart viewer.
His article has screenshots of gps displays which are missing the ledge around the daymarker. A fireboat belonging to the city of Portland suffered $90,000 in damage while returning from a rescue in this area in Nov. 2009. (see related news article
While you are there, check out the cover photo on that Points East Midwinter issue. That's one on my photos!