This is an amazing idea. I’ve toyed with the idea of creating both subject specific and geographic specific groups for my interests but it’s a clunky solution. For example, I like birdwatching, but I want to know what people are seeing around me, not on a continent away, so being able to join a centralized ‘birding’ group then narrow it down geographically would solve the problem of having to create potentially hundreds of sub groups. Same for politics, news, restaurants, etc.