[Jamz]

I would have to give this a +1 as well.

For instance, I'm GM'ing RotRL and for #reasons I've limited my players to CORE book only (and 1 campaign setting book).

So when there is an update, there's a chance that my players are adding spells/feats/items that are illegal in my campaign.

As a side note, something as a wishlist for PFO, it would be great if there was a "campaign" option online that would let a GM set options/books/etc and other players could subscribe/link to and would lock in those settings for a given character...