1. A method for categorizing users, the method comprising: maintaining a list of identifiers that are selected by a first user and for which online presence information is made perceivable through the list, the list including one or more categories into which the identifiers are categorized; accessing at least one attribute associated with an identifier for which online presence information is to be made perceivable through the list; accessing attributes stored relative to at least one of the categories; comparing the attributes associated with the identifier to the stored attributes; based on results of the comparison, identifying at least one category within the list that corresponds to the identifier; and categorizing the identifier into the identified category.