I'm a mechanical engineer designing products on a daily basis. We have a (really good) 3D printer and pump out amazing models all the time. Our's uses a fairly strong plastic and allows for things like moving linkages and very fine detail. The models are an amazing aid to communication and design. But ultimately they won't change our manufacturing process - the materials are too weak for our needs. So we make prototypes out of plastic and then the actual manufacturing run will be metal.
That really points out the problem with these columns that suggest 3D Printers are about to drastically change manufacturing. These 3D printers are only really a manufacturing revolution to people pumping out plastic (or weak powdered metal) products in low volumes (<1,000 units) and sizes between a few mm and meter or two cube. That actually doesn't cover a whole lot of products - the unit numbers are the thing that rules out most things you would think of.
3D Printers are great in the design phase - but a contractor like Shapeways will ultimately benefit the most from that.
Actual manufacturing of products was disrupted far more by CNC control. Truthfully a 3D Printer for all it's fancy tech is just an extension of CNC machining into building up from scratch instead of cutting down from stock.
CNC changed everything. You can CNC machine shapes that would have just been impossible before, on a size scale that no 3D printer today can match. You can use any material, and you replace REALLY SKILLED labor (a machinist) with a machine. That was dramatic. The 3D printer is just small potatoes compared to the change that has already happened over the last 30 years.