That's just cross-side network effects. More users is better for hosts which means more hosts which is better for users which means more users. What you probab

That's just cross-side network effects. More users is better for hosts which means more hosts which is better for users which means more users. What you probably have in mind is "direct network effects", more like what you'd see with a chat app or social network (though social networks also have cross-side effects between users and advertisers).