I don't know if this is technically a bug... but in my current game I am playing against a team of four AI races and several times now I've had the AI asking me to go to war with them against one of their teammates, or trying to pay me to attack one of their teammates. Now while I guess this could be seen as totally awesome and sneaky faction politics (I can't attack this guy, but I can pay someone else too) it really doesn't seem to fit how a team should work.