There's an excellent article about photography, art and museums over at LL:
Are Museums Destroying Art?
I've never understood the need to take photos of two-dimensional art except for archival use, since the photograph will never add anything to the image. But there's more to this too. The article also shows how the value of the snapshot is approaching zero. And while the esthetic value of snapshots can be discussed, their role as documentation is important as a mirror of the times we live in. Now, they seem to become the photographic equivalent of the Mayfly; One moment, it's taken, the next, it's gone