Just as clarification of the linked article, I understand that Nat Geo changed its mind after a quiet word with the Facebook/Instagram brain-trust. Though I'm not sure why.
I am more concerned about the Terms of Use that leave the poster on the hook for any claims arisising from lack of model releases, etc. Not only do you not get paid for use of the image, you have the joy of defending/paying any claim filed regarding use of someone's image (imagine, worst case, that bloke you snapped in Times Square is a recovering alcoholic who finds his face in a liquor ad licensed by Facebook from your Instagram post). As I've pointed out elsewhere, Facebook paid a ton of money for Instagram, and they'll eventually face pressure to monetize its database. But my girlfriend says I'm unduly cynical...