Built in Decoherence for safety
Without proper safeguards, a very larger server sky system could be used as a microwave beam weapon. While one array will not produce enough power density to kill somebody, it is possible to imagine some malevolent system cracker or some rogue military power turning the beams from thousands of arrays onto one spot, cooking everything that is not shielded.
This can be prevented with proper design. But I don't know the best way to do it. It should be failure-proof-by-physics, not by programming. Imagine, for example, that the only way to connect to a location to the ground is in response to a guide beam from the ground; otherwise, an array is unable to coherently focus on that spot. Perhaps the guide beam generators shut down or fry when the power density exceeds safe levels.
This needs to be thought through. The safety systems should not only be physics-based and failsafe, they should also be easily explainable to the public.