I like the idea of being able to turn it off and on so that guild members can practice pvp with each other. I also like the idea of being able to turn it off and on with alliances as well for the same thing. You can't have constant pvp between allies because the leaders will constantly be having to monitor and police the dicks that guild hop just to cause problems between guilds. There is no amount of interviewing or vetting that can prevent these kinds of people from joining guilds just to create issues within them. Leaders can only react to their havoc they cause which can then be an everyday tedious chore.
I would like to see options of banning accounts from guilds as well so that players who try to do this with one character are then prevented from bringing in characters under other names.