I've recently started a thread about editing EXIF GPS tags in my images from Expression Media. Microsoft has taken the stance EXIF data is read-only and GPS tags fall within this category. The referenced Wikipedia link lists a number of problems with editing EXIF data so maybe this isn't entirely unwarranted.
The majority of tags edited post-capture are handled by IPTC but unfortunately the GPS set of tags reside solidly in EXIF. Since I can't update my geo data from within EM I can, and do, edit it with other tools, namely PictureSync or the amazing ExifTool.
So who's right? If EXIF data is meant to be static, and for the most part does contain static data, then MS has a somewhat sound argument. But if the rest of the industry eschews this notion then should MS really decide otherwise and inconvenience its user base?
Standards work best when they are.