Especially if you have a larger forum with many users and pictures.

Check out this: PhotoPost Community - View Single Post - Spider Friendly URLs are not 100% spider-friendly.

6300+ urls blocked and I know I missed a few to block and there are some I can't block with out blocking out legitimate pages as well (due to the url structure)

I really, really hope vBulletin comes out with their own gallery soon. This is ridiculous.