Right now the system for browsing tags is a bit simplistic (hey, we're in beta!), and people are getting frustrated over tag spam.  So right now, it is whatever the community of the tag you use decides.. and some people, like me, are picky about their favourite tag.
Since your other post did not have original photography, I would argue it probably shouldn't have the tag (by the way, you can edit your post to change tags if you desire).