3D printers actually show that there is no limit of the technology. If 3D printers are used to the advantage of people can lead to great results. For example, technology revolution in medical can be realized. In these areas, cheap and accessable opportunites can be created by experts.
On the other hand, anyone can produce weapons in their house. Malicious people or terrorist groups can use this 3D technology against the other person or group in accordance with their own interests and it does not have a limit. Consequently, the future that filled with great opportunities and dangers await us.