It's a good question, as I have seen someone who opened up a can of worms in the religion forum only to have no hubs himself.
However, there are those who could be just active readers without hubs and actually participate.
If I am correct, I think that readers are encouraged here just as much as writers are. So, I suppose HubPages would have to leave that door open.
It would be nice if one of the HubPages Elite could qualify this however.