3D printing might halt development in the developing world and inhibit societies there from becoming wealthier and more democratic.
Ultimately there is no money in 3D printing. Meaning, that it will suck the value out of any and all manufacturing while becoming cheaper approaching the point of free. This might lead to mass unemployment or at its most extreme the cessation of much of the economic activity on this world.
By decoupling people from companies, states, society at large 3D printing might accelerate our current trend towards ever less trust in each other and institutions.
Criminals could use 3D printing for crime. As ATM scammers have already done.
The 3D printing bookof accurate face masks that resemble other people would wreak havoc on the way crime is fought now and make all witness testimony unreliable. How do you catch someone if you don’t know what he looks like? If he’s discarded his fully articulated realistic face mask to reveal his own face or perhaps even another mask beneath and then enters a crowd. Face Off, All the time.
If machines without recyclable materials predominate then impulse 3D printing could cause an adverse environmental impact.
3D printing will make terrorists & spree killers more powerful and will also let armies iteratively improve their war fighting capability.