These items will only be sent to people within a certain radius of distribution centers and are only for a specific delivery window: 30 minutes from order time to delivery at your door. You have to select this option, and I'm sure you wouldn't do so if you won't be at the house.
As to jobs becoming obsolete, that's just how things are. That's part of progression, and further, movements of this type are of value as they mean less strain on non-renewable resources and less overall strain on the environment. We don't have milk men anymore, but we've all survived.
Further, this rollout will not be until at least 2015 or later. Dinosaurs will die and change is inevitable.
It is stated in the story that this is for the majority of packages the company ships, which are under a max weight limit. I don't think a secure drone touching down is going to be a bigger risk than the normal slamming and banging that is seen from packages being moved around the city by UPS, FedEX, the USPS, DHL, etc.