Except it does, if you have a sufficiently convincing reason for people to opt-in. Since a few weeks, our hackerspace - which used to publish all door unlocks

Except it does, if you have a sufficiently convincing reason for people to opt-in. Since a few weeks, our hackerspace - which used to publish all door unlocks on IRC with the nickname of the person unlocking it, by default - requires opt-in for nicknames to be published. People recognize that this is an important social function of the space, because it ties together the IRC channel and the physical space, and thus the vast majority(!) of members have explicitly opted in. This whole narrative that "if you make it opt-in, not enough people would ever do it" always conveniently leaves out that that's only true for things where people don't want to opt in, ie. usually things that benefit the service but not the users.