Advertisers. They are intensely curious about how the human brain really works.
Generally, any group making stuff that somehow hangs together even without profit motive.
They make stuff--so they can't just only be "social". The group continues to exist--so people find it interesting enough to continue joining. It's not making a profit, so the group has to have something of worth beyond pure monetary value.
The big problem right now is simply finding those groups because they often aren't advertising themselves.
I remember one of the guys, with no prompting, sharing a map with me showing that there was something like a 2 byte/second emergency radio link between wherever he was and Melbourne.