If a group is larger than it needs to be it can lead to social loafing. Check a group communications text for more info on social loafing and group dynamics/communication

Social loafing is the occurrence where people in a group setting appear to exert less effort in completing a goal or task. This is seen as a diffusion of responsibility amongst the members.

Social loafing refers to the tendency for individuals to exert less effort in group settings compared to when working alone. Social facilitation, on the other hand, is the phenomenon where individuals perform better on simple or well-learned tasks in the presence of others. In summary, social loafing is a decrease in individual effort in a group, whereas social facilitation is an improvement in performance in the presence of others.

Steps to reduce social loafing might include assigning specific jobs to each person rather than allowing them to work together as a team. Also, confronting the social loafer can help to correct the behavior.

it's unclear whether by "social loafing" you mean people who do not socialize much, or people who do not work much--and therby rely on society for support.

Note: To clarify (but not to answer, as I'm not well-versed enough), "social loafing" is the phenomenon where someone who's usually productive on their own starts slacking whenever they're in a group.

Hope that helps.