Delivery, monitoring, search and rescue, emergency radio relay etc... the possibilities are many and expanding.

RE Shoot downs : Retrieval becomes difficult if the product is fragile as well. I imagine these devices will contain some sort of distress beacon and/or continuous transmission of its coordinates to a base station.

400 Feet (approx. 122 meters) is the current altitude limit in the US, I think. Birdshot is inaccurate at that distance and it's quite a height to try and shoot at relatively fast drone with a rifle. This is in addition to the fact firing recklessly into the air carries hefty penalties alone.