I think this is probably implicit in the game to an extent. Though the GM is primarily responsible to set Obs, he must do so fairly. This is enforced by the rules and group consensus. So if the players call him up on a rules mistake, the GM should listen. I am not sure there is much to gain from shifting the GMs role to set the Ob first, though it could be interesting to find out.
Just wanted to thank you for the link to your LJ page – I explored all the outside comments related to BE as well and it was super-interesting! We’re having similar issues at this end, particularly with a single player who clearly has a stronger grasp both conceptually and tactically on what’s going on than anyone else playing.
Old-skool GM wants to balance everything out and make sure everyone gets their fun. BE GM wants to push the characters into squabbling so I can hull the lot.