When somebody mentions 3D printers, some may think this is the first step towards a star trek replicator. They are probably right. 3D printers will change the world as we know it. Mostly they will usher in a new era of open source hardware and piracy.
Imagine a world where you can download a design for a new ipod, and print it out within seconds.
Imagine a world where there is a thriving open hardware movement to complement today's open software movement.
A bit farther off, imagine downloading a recipe for an entree from a five star restaurant, and then print it in front of you.
What would happen to all the jobs built around the concept of design once, sell many... especially when a hardware design can easily be pirated?
Food and Clothing jobs will eventually change significantly, but chefs and fashion designers will remain for the foreseeable future.
Entertainment will not change a whole lot and still be complaining about piracy.
What would happen to FedEX and UPS?
Shipping services would most likely be relegated to raw materials and perhaps goods made with volatile materials.
How far off is this?
It is hard to tell... but a decent guess would be within 50 years, but it could happen as early as 30 years. You will start seeing the signs of these trends in less than 15 years, although you can see them right now if you look closely enough.
So lets look at the printing of food for a bit and take a few logical guesses about the future here. The thought of whipping out your HP printer and printing out a nice juicy New York Steak and Eggs is probably not going to happen, at least not in the form it exists today. However, the machines could build "flavor" molecules which act as spices or when heated and with water could produce various textures of certain types of food. These machines would more be of the simulation of foods rather than the production of Angus Beef.
Why would anybody want a simulation of a steak rather than the steak itself?
When humanity expands out into space, those space dwellers aren't going to have the amount of land necessary to support cows. Its simply too expensive. However, having one of these fancy simulation machines can trick the person into believing he is eating a Kobe Steak.
So in conclusion, would this technology change the world for the better? I think so. It allows people to experience the entire range of life, and for very little money. Anything that improves the lives of the entire human race, I think is a good technology to have. Even though it can and surely will be misused, its potential for good is too great to ignore.