Didn't note which forum I was in.
I am not too sure of using the meta data for confirming a site visit, for a start its very rare to have a camera with a GPS embedded in it (except new ones) and if you are using a computer to merge a photo and a gpz file to append the meta data, the camera and gps clock needs to be almost exactly the same. Out by 5 minutes can make the distance errors massive at 100 kms per hour. Its also dead easy to edit and modify exif data back at home, so it seems a little bit redundant to me. I am mainly concerned that having a georeferenced photo might be unachievable to most.
An alternative option could be to make it mandatory to add a photo to a log when logging this type of cache and give owners the power to delete logs that do not comply, maybe?
Indeed I geotag all my holiday photos retrospectively, by syncing them with my GPS tracklog after I return home. My digital camera and phone don't have the capability to tag photos as I take them. I could tag a photo as being whereever I felt like it.
I like teh idea of the "Creature Cache", not because of the technology (as I think it is basically a virtual with extra demands), but because of the special nature to mark it appropriately.
A sign that you have done these well enough would be when National Parks pay you to set them up!
I think the technology of using photo meta-data would be a bit difficult because the number of people with GPS enabled camera's is quite limited. I am sure the traditional methods would suffice (al-la Earthcache).