Populating users of a web community into groups. The users may be assigned to, or otherwise associated with, one or more groups in response to an event associated with the user, with another user, with a group, or other type of event. The users may also be removed from a group in response to an event. The population of users into groups can be controlled by a configurable set of rules. These rules can include criteria for associating a user with, or removing a user from, a group in response to an event. The criteria can include criteria based on user information and criteria based on group information. The users may be related to one another in a hierarchical structure.