The reasons varied, even in other studies I looked at. From memory, from the interviews I performed, some cited an issue with social status (e.g. loss of friends, family etc.) if they expressed their views, and others identified certain topics as taboo (and so they didn't feel the ability to mention them in polite conversation). What I found as doing the interviews, though, was that people are good at acknowledging that they find certain topics uncomfortable, but generally aren't good at acknowledging explicitly self-censoring. Empirically, we know people do this - Das and Kramer (2013) did a study for Facebook finding exactly this, that there is a phenomenon of people just typing out comments to post and then deleting them - but there is also a barrier in getting people to acknowledge that they, themselves, self-censored. I came to understand this as I performed the interviews: (1) We live in a culture of liberty and individualism, which means people might have difficulty even acknowledging that they might be hiding their own views; and (2) If people *did* have views they wanted to keep hidden, they have no reason to trust me (as interviewer) any more than the folk on Facebook, especially since I knew most of the sample (a bad research design I chose specifically in the hope that that meant participants would confide more in me), and the ones I did not know I still had names and contact details of. In the end, the most valuable data came from asking about "other people" and hypothetical scenarios. Across the board, people interviewed acknowledge exercising explicit censure on other people who expressed disagreeable views. In many cases, they had personal examples themselves of disassociating from close friends over different views. They could also imagine scenarios (often posed with specific people the participants knew) where they would disassociate from other people based on statements made. Some of the hypothetical scenarios were understandably excessive - while most of the participants acknowledged hot-button political issues whereupon they could no longer be friends with people who disagreed, other people only started expressing reservations once topics such as paedophilia or explicit opposition to the participant's or other people's identities (ethnic, sexual, gender etc.) came up as potential topics. It seems it is always conceivable to find *some* group where it would be impossible for any given person to get along with the participants of said group by nature of their existing - and that seemed to be one of the findings of my own research. When people have beliefs or identities they are passionate about, it can be hard to impossible for them to imagine being friends, associated with or otherwise tolerating people who hold the opposite view with an equal passion.