[ahartman00]

"ask the makerbot for kilograms of RDX or tabun instead of a gun"

I know the NSA and IoT get a lot of criticism here. But this seems like a good usecase for the always connected, phone home systems, with an all seeing eye. :)

"killers are pre-empted by omniscient benevolent AI oversight"

As someone who used to work in a warehouse, ai which can detect anomalous orders seems incredibly plausible. Considering they have all been storing data for years, you have plenty of training data. Making something that notices when certain substances are shipped to someone who is not a normal customer seems trivial, if it doesnt exist. I mean the conservation of mass means that the explosive has to come from somewhere :)