Intergroup Conflict and Cooperation
When a group forms, the members of that group develop not only a sense of belonging to the group, but also a sense that others do not belong to it, and develop a desire to protect and defend the group from outsiders - particularly, those who belong to other groups.
THE ROBBERS CAVE EXPERIMENTS
An experiment was conducted in a wilderness setting, two groups of boys were sent to camp in separate areas and kept carefully seaprated. Upon discovering one another, each group coalesced (the cliques within the group dissipated, and they gained a group identity) - and the two groups then became hostile to one another.
When the experiment degenerated to the point where the boys were beginning to attack one another's camps, the experimenters attempted to get the boys to work out a truce , ultimately succeeding only when they presented the boys with common goals (a broken water supply) that could not be solved by either side working alone.
INTERGROUP RIVALRIES ON THE INTERNET GAMES
One example from internet gaming shows that individuals on randomly-assigned "teams" tend to support their team-mates and oppose members of the opposing team - without knowing anything else about them. When the same group is re-hashed, the players will pull for team-mates who were previously on the other side, and rail against former friends who are now in the enemy camp.
The emergence of "guilds" in online gaming is another example of group formation and intergroup rivalry: teams of players form to help one another, but invariable end up becoming hostile and competitive toward the members of other guilds.
Many of the psychological principles underlying group identity and cohesiveness are also used by such guilds: they have requirements for members that must be met in order to join; they have a formal initiation; they require certain behavior to remain a part of the group; they have clearly delineated standards of conduct; they exploit intergroup rivalries (even insofar as seeking to "kill" members of other guilds) to reinforce the cohesion of their own members.
Intergroup rivalry has become a concern of some server administrators, who find that rivalries among guilds have been detrimental to attracting new players - but at the same time, steps taken to discourage the emergence of groups and competition among them has been detrimental to the retention of players for whom their group identity is one of the rewards of participation.
Some discussion of personality types in online gaming (achievers, explorers, killers, and socializers) are identified, but I think this is peculiar to gamers, so I'll skip it.
INGROUPS ON THE INTERNET
Outside of gaming forums, "groups" evolve on the Internet in other venues. Primarily, people are brought together by other factors: their lifestyle, hobbies, and professions.
One factor that differentiates people, and which is fairly easily identified, is a level of expertise. This may be technical expertise in a specific skill, or something as simple as experience being a member of the group. This leads to a form of elitism within a group - the cohesion between experts and the group elite, and a disdain for novices and newbies.
INTERNET GROUP POWER
The internet has considerable power as a medium for coordinating the efforts of large numbers of people.
Anecdotal evidence is provided that show how the Internet can be effective in coordinating community protests - reaching a large number of people and incenting them to protest a government action or boycott a company's products.
Note that this is not the same as the formation of an ongoing "group" in the social sense, but the motivation of a large number of people toward a singular purpose for a short amount of time.
GLOBAL VILLAGERS: ARE WE A GROUP?
There is the sense of the entire internet belonging to a single group. However, the author disagrees with this assertion, and does not believe that a single homogeneous group will evolve:
Primarily, groups form because they are like-minded individuals - hence, similarity is a prerequisite for group formation, not a result of it.
Also, the members of a group form a cohesive bond with one another that also serves to separate them, not unite them, from other groups.
Finally, there is the growth of the Internet itself, one primarily the venue of a very specific demographic (young, educated, professional, white, male), has become more heterogeneous. And while such qualities as gender, age, race, and income are not evident in the medium, they do tend to drive a person's interest and lifestyle, and thereby have an influence on the groups a person chooses to join (or not to join) online.
If a global mindset evolves, the Internet may contribute to it - but from a psychological perspective, the Internet does not have the power to be the cause of such a change.