[jpatokal]

The article directly contradicts your claim:

While the hardware is a significant part of the problem, they seem largely agnostic about which flying machine might ultimately serve their needs best. The real challenges, Teller and Roy insist, come in the design of the rest of the system like, for example, the delivery mechanism.

For example, the reason they do the winch down thing, instead of just landing, is so that customers are not tempted to approach the drone and get hit by the rotors.

[hnriot]

instead they get hit on the head.

[ynniv]

... by something lowered on a tether. If you think that's comparable to touching a rotor, you don't know much about rotors. mv^2!

[hnriot]

touching a rotor chops your hand off. Getting hit in the head by delivery of dog food kills you. It's kinetic vs potential energy. for your kinetic energy equation you need a lot of speed and a lot of mass. You can have one of those, but not both.