3D printers have been around since the late 70's/early 80's. I used to work for a large computer graphics company and they tried to acquire the manufacturer of the system. The generic term for this type of technology is stereolithography. The system used a liquid polymer which solidified.
Oh, never mind, they are just covering this in the podcast. I can add that the system sold for hundreds of thousands of dollars at the time.
I've used the technology to make prototypes. It's fairly costly on a per piece basic, the materials you can use are limited, and they are slow compared to volume production methods like injection molding. But you can make a really nice prototype and make sure everything fits together and take it to a trade show or focus group much quicker than using tooled parts. Tooling cycles used to be 6 months plus for the parts we were making.
The reason it's called additive is because it is the opposite of milling, which is subtractive. Semiconductors and MEMS are made using both additive (deposition) and subtractive (etching) processes.
I don't think we'll ever see a machine that can spit out an iPhone. It would even be difficult to use it to manufacture replacement parts as was suggested because the materials that can be used are limited. I'm not sure how the stereolyth materials match commonly used materials like ABS nowadays. Maybe they do, I haven't kept up with the field.
The Maker stuff is pretty cool.