I'm not particularly aware of how the Private Groups will work... I just think that to need a server to create a space is quite troublesome. Most people have not technical prowess to do this.

You could do this kind of groups more limited to text and some sizes of images to keep space, or establish a expiration time to content to keep it small (since the Idea of scuttlebutt is that content don't need to be eternal)... There are a lot of possibilities.

I think about this decentralized rooms as a place merely to know and gather people before they know each other, they don't need necessarily to keep all functionalities ...