Finally getting around to reading Rule 34 (now in paperback!); I'm 3 chapters in and it's gotten into black market 3D printing. It's fascinating stuff. Minor spoilers follow.
Stross posits a near future where 3D printers are commonplace but come stock with DRM to restrict the things people can print. Stripping the DRM is easy enough; so is getting onto a VLAN through an illicit wireless network whose transmissions are disguised as line noise on a voice network. The fab plant is compared, pretty immediately, to a drug lab, and the guy running it is paranoid as hell about getting caught by the law and, of course, in debt to various criminal organizations.
Stross's version seems to indicate a much more complex machinery than just "plastic goes in, plastic comes out"; he extends the drug metaphor by having various different chemical ingredients sold illicitly by seedy dealers.
Homemade guns are mentioned in passing, but, well, the book (1) is called Rule 34 and (2) is not a comedy (or, alternately, is a REALLY FUCKING BLACK comedy), so the focus is on 3D printers being used to produce some pretty stomach-churning stuff.
I imagine the book's going to get a lot nastier as I go, and I can't say I'm looking forward to that. But it's definitely one more example of Stross looking at tech and society and putting a hell of a lot of thought into what could realistically happen in the near future.