None. It would likely not be an issue. But your example is irrelevant because there are now laws, laws created because of people doing as you describe.
But, because others have flown their drones in more precarious situations, specifically around airports and at the same altitude as passenger jets at close range, the laws have now been set. So now, if you fly your drone around Niataga Falls you would be contravening the laws and the governement would then have reasons to make them more strict.
I am sorry these concepts are lost on some of you. But if you either a) fly irresponsibly and b) break the laws, the laws will clamp down on the rest of us. The risk is a total ban on drone flying. Don't be a selfish jerk about it and THINK before you fly and follow all the laws and rules and outside of the laws, fly responsibilty - I guess you need a definiton of what "respoinsible" means - it means "flying such that there is no risk that your actions will cause further restrictions on the rest of us responsible drone fliers".
It's not rocket science. It's simple consideration and intelligence.
The law is now no flying around Niagara Falls. So don't fly around Niagara Falls.