Social fragmentation and widening disagreement among constituents have become a highly relevant and critical issue in our modern society. Such a trend may be understood as a consequence of (undesired) social self-organization facilitated by various sociopolitical and technological factors. In this talk, we will review our three recent modeling projects on this subject, addressing (1) formation of extreme ideas and social fragmentation caused by social conformity and homophily in adaptive social networks, (2) intensified disagreement among opinionated groups due to people’s enhanced ability of information gathering, and (3) how those problems might be overcome by social constituent diversity.