Due to the super federated nature of pump I could Groups being an instering technical challenge to implement. Maybe as a psudeo user on the originating pump that people follow and post to. But then that group is tied to a single pump and not really federated. If that pump goes down the group evaporates.

I suppose a group property could be added to the note object. But then there is little or no control over who can post to a group

Other problems, how do you prevent group name colissions? Keep track of who's subscribed? And do all this in a robust, federated manner.

Suppose there could be some kind of “groups” object that gets replicated and stored on each pump that has people sub'd to said group. But then how to keep it all in sync..

@evan is a bright person, I'm sure he has a vision of how it will all work.. but I know (as does any programmer/engineer/etc.) that vision and implementation are two very different animals.

Best advice:

People wanting groups - wait for it.. it'll come
People Developing pump.io - don't cave to the pressure of the few and rush something out prematurely. I think the larger percentage of users are very appreciative of what you've accomplished and want to see it fleshed out properly