Let's take 3D printing to the circuit board world.

A consumer machine that can be configured to takes as inputs:

1. A set of different electrical part. (Perhaps self-contained in a large box like printer ink is)

2. A circuit board schematic file

The machine cuts the board and solders the parts in.

And there you have it! Your own computer factory! (For limited definitions of "computer")

If this idea ever piques anyone's interest, I'd love to lend a hand with it.