Imagine, printing solar panels for your house that are nearly 100% at converting solar energy to power - at almost no cost. Fabricating food at will. "Printing" the latest computer designs - that possibly embed in your body and can, among other things, constantly monitor your health. Computers that run faster than anything you can imagine. Even printing out replacement organs. Or even an entire replacement body.

http://crnano.org/benefits.htm

"Overview: Molecular manufacturing (MM) can solve many of the world's current problems. For example, water shortage is a serious and growing problem. Most water is used for industry and agriculture; both of these requirements would be greatly reduced by products made by molecular manufacturing. Infectious disease is a continuing scourge in many parts of the world. Simple products like pipes, filters, and mosquito nets can greatly reduce this problem. Information and communication are valuable, but lacking in many places. Computers and display devices would become stunningly cheap. Electrical power is still not available in many areas. The efficient, cheap building of light, strong structures, electrical equipment, and power storage devices would allow the use of solar thermal power as a primary and abundant energy source. Environmental degradation is a serious problem worldwide. High-tech products can allow people to live with much less environmental impact. Many areas of the world cannot rapidly bootstrap a 20th century manufacturing infrastructure. Molecular manufacturing technology can be self-contained and clean; a single packing crate or suitcase could contain all equipment required for a village-scale industrial revolution. Finally, MM will provide cheap and advanced equipment for medical research and health care, making improved medicine widely available. Much social unrest can be traced directly to material poverty, ill health, and ignorance. MM can contribute to great reductions in all of these problems, and in the associated human suffering."

But there are risks too. If you think computer bugs are a problem now, just wait until somebody puts a "virus" in your body embeded nanocomputer that also contains a micro amount of a highly toxic compound. Most people have no idea how deadly VERY small amounts of certain compounds can be. The risks of those compounds would be very real if anybody could "safely" make them at will. These risks, and others, can be mitigated somewhat but when everybody could, in theory, "print" guns - or even nuclear weapons - it is clear that the consequences of this are staggering.

http://crnano.org/dangers.htm

"Overview: Molecular manufacturing (MM) will be a significant breakthrough, comparable perhaps to the Industrial Revolution—but compressed into a few years. This has the potential to disrupt many aspects of society and politics. The power of the technology may cause two competing nations to enter a disruptive and unstable arms race. Weapons and surveillance devices could be made small, cheap, powerful, and very numerous. Cheap manufacturing and duplication of designs could lead to economic upheaval. Overuse of inexpensive products could cause widespread environmental damage. Attempts to control these and other risks may lead to abusive restrictions, or create demand for a black market that would be very risky and almost impossible to stop; small nanofactories will be very easy to smuggle, and fully dangerous. There are numerous severe risks—including several different kinds of risk—that cannot all be prevented with the same approach. Simple, one-track solutions cannot work. The right answer is unlikely to evolve without careful planning."