Do we really want a world where even the skies are full of ads?
It has crept into virtually every other place - your TV, the sides of football pitches, the (virtual) turf on american football fields, etc. etc.
In this case at least, fleets of drones couldn't really be used over populated areas due to the risk of a failing drone falling and hurting someone. So I don't expect to see too much of this in most areas. I'm sure we will see it over sports arenas when the area under has been temporarily emptied of players.