If you look at it a certain way, this is what email was before ISPs and bigcorps gave away email addresses; everyone who had an email address was paying their sysadmin for the privilege of having one (through their tuition at a university that has email services, or through the cost-center of the company they work for.) In either of those cases, people were more careful with email, because postmasters were easily angered (and this was, in turn, because causing trouble could actually get your system kicked off the network!)

In modern times, people pay to use Slack. It'd be interesting to study the sociology of paid Slack groups (as compared to free Slack groups, or as compared to any other free-for-everyone group chat platform.)

I've always thought it'd be a cool idea to have a group chat platform where, rather than some admin owning the group and maybe paying, the group has a tip-jar and anyone/everyone in the group can contribute. (Twitch sort of works like this, but you're really donating to the channel owner, not to the group itself. In my hypothetical model, there is no channel owner; the group persists because at least some of the user-base want it to, and so pay for it to.)