A score is generated for each of a plurality of potential user groups in which to add the first user, each potential user group containing a plurality of users, the score based on a location of the first user. The first user is added to a first user group based on the score generated for the first user group. A pinning action by the first user pinning the first user to the first user group is then received. A change in location of the first mobile device is detected, and the score of each of the potential user groups is regenerated based on the changed location, causing a determination that the first user should be removed from the first user group. The first user is maintained as a member of the first user group despite the determination that the first user should be removed based on the pinning.