I would like to ask about a somehow related issue: the small balloons with cameras.
This hobby has became popular recently and I wonder to what extent it is safe?
Not particularly safe at all. It is a big sky, but the payload looks to be large and dense enough to damage an engine/or dent an airframe.
If this is not using a transponder to report its presence, air traffic control would have issues with it. Is it insured against damage to others? The participants might be getting a knock on the door from the government when they realize just what is going on.