Yeah, could be many reasons for this. Most likely one is that the location data supplied by the individual monks isn't that accurate. For example, when I checked my own I was also out in the ocean. The good thing about Google Earth is that you can use it (in many areas) to zoom right into the building you work/live in and get an accurate fix (which I did with mine, and updated my home node).
One other possibility is that some Monks (such as tye) like to play funny buggers and pretend that they live at the South Pole, or other similarly "exotic" locations ;)
Of course, some others may not be comfortable with the idea of supplying "precise" location data - which is fair enough also.