Unless there's more involved in "ritual" whatever than just standing in the same room togther, I'm not a big fan of the idea. Of course, I'm not a big fan of more of the same, but innovation, so that might be coloring my thoughts on the matter slightly.
It would be nice if there were reasons to congregate and interact beyond the economic and resource sharing that usually binds groups together though. What would be the point of ritual casting as a whole though? Is it just more powerful spells and skills, or is there something that requires more than one person to complete it? I could personally get behind areas or quests that used ritual <casting/skilling(heh)/whatever> to accomplish some lofty or difficult goal (rolling a huge boulder out of the way might be too much for any one person to do, but two people might be able to... or just have rediculous stat requirements for such a task so that it's unlikely less than two people could accomplish it) but in the general everyday sense I think it wouldn't be very special at all.
