For what it's worth, working with images is what I do all day. I own a small business where I work with digital images in various programs. I could easily stitch together multiple images taken from differing vantage points and no one would be able to tell.
I do not offer this as any kind of proof of altered or real images, simply that it is possible, with relatively inexpensive equipment and a decent amount of training and ability.
After having done this for many years, I have learned not to trust images put before me, unless I can, to my own satisfaction, verify how they came to be.
I find it rather silly that this whole Toronto skyline photograph issue keeps rearing it's head as though it has any real meaning or proof.
For me to give any of these photos any credibility, I'd have to be reasonably convinced of their authenticity.