Common forms of CMC include email, electronic bulletin boards, online conferencing, and the Internet. The first network-based CMC system, the ARPAnet, was developed by the US government in the early 1960s. The ARPAnet was created by the Department of Defense to enable geographically dispersed people to communicate in the aftermath of nuclear war. Other governments have used the ARPAnet model to disseminate political information. With these mainly political motivations, the PEN is intended to increase the effectiveness of government services, improve interactions between citizens and government, and increase citizen participation.
BBSs are closed systems that generally reach a limited geographic area.
Most are begun by computer hobbyists who want to play with technology and communicate with people of similar interests, and the content of BBSs generally reflects the specific concerns of the members. These systems do not support the most complex forms of information, such as realtime sound and moving graphics, and are mainly used to post and access information. Although some may offer some information content of their own, commercial ISPs are generally used by members as a platform to reach other areas of cyberspace. Although these networks provide many of the services offered by other CMC systems, the distinctly local ownership, audience, and focus of the content separates community networks from other systems. Because community networks are rooted in physical communities, social goals, rather than strictly economic or technological motives, play a central role in their mission.