Figure 2. Mobile communities lie within a space defined by two dimensions: focus of community goals and community longevity or stability. Mobile communities in the first column (1 and 3) focus on financial goals (more explicit transactions), while those in the second column (2 and 4) focus on social goals (softer, less tangible exchanges). Mobile communities in the first row (1 and 2) are longer-lived and change slowly, while those in the second row (3 and 4) are shorter-lived and more ad hoc. Most people are members of all four types of mobile communities.