I've been thinking a bit about this post about groups that @Kiloku made yesterday, and about how we'll be able to figure out when it's the right time to create a new group.
I had an idea (inspired somewhat by how StackExchange's "Area 51" works), and just want to see if you all think it's worth trying sometime, or if there are reasons that you think it wouldn't work very well.
Every week or two, we could have a thread for "group proposals", where people suggest groups that they think would be good to add and likely to be active enough. If there's enough support from other users (for some meaning of "enough"), we create the group and then give it a while (maybe 2-4 weeks) to see if it actually builds up a reasonable level of activity. If it does, great. If not, we could remove the group and move the posts back into another group with an appropriate tag.
So for example, if someone suggested a group for fantasy novels and a decent number of other users express interest, we could create ~books.fantasy as a trial. A few weeks later, if it doesn't seem to be working out, we move all the posts from it back into ~books with a "fantasy" tag (and can always try it again in the future).
I don't know if we'd want to do this anytime soon, but I thought it would make for an interesting discussion anyway, so let me know what you think of the general idea.