I have experienced leaderless teams in my career (46 years) a handful of times. They formed around a problem that was unrecognized by Management (thankfully) but need to be solved. My best example was at a large SW dev firm in the late 80s. World wide electronic communications was need and faxes and leased lines connected to Decwriters were not good enough. I was assigned to the task as just one of my responsibility. A Single 1200 baud access to internet email at a university solved the problem. The problem expanded many people wanted the same service so we need someone (team member 2) who had access to a UNIX systems. Eight serial ports and 2400 internet connection to the first local ISP.

Rinse repeat 5 years later 10 people, part time, supported all internet connections and intranet/internet web-servers including application without management sanction. Everyone had a service role in there own department. Being connected to the others meant we performed at a high level. We didn't have a leader per se but we all moved in a common direction.

It lasted 8 years and finally several Directors discovered we existed as a team. Like sharks they each took a bite out of us, each one trying to become the dictator of the internet. Procedures were imposed. We were not allow to speak to each other with out going through the directors. Our individual productivity dropped. Angry internal clients screaming for the old way. Nothing got done. Three months later the director that won got half the people back together but we were not the same any more. I still found interesting work for 2 more years before finally leaving.

Leaderless teams can work under the right conditions. I have tried to create them when I moved into management and it worked to some degree a few times. I did not lead or participate in the teams I just suggested people talk to each other know that the might click. I fed them problems (and resources) that I knew that they could solve that I knew would take more effort/time if we did it though channels. The individuals got recognition and I got my problems solved.