I ask the DM what is available, and the DM sets the limits.
Ingame, the entire game is the DM.
Qft. However the way the rules are set, I don't think the DM is doing a particularly good job all the time.
This kind of balance is important to BGS, just look at past games and see how bad it was.
Ex, anyone grind magic spells in DF simply by throwing Destruction spells into the wall and absorbing the magic?

Those times are gone, because they were
easy to abuse. The intentions were good but the outcome bad.
I don't care if things can be abused, as long as the rules makes sense and I don't abuse anything without even trying.
For the scaling of effects, I've always been against this whole additive stacking business. The maximum outcome potential should be twice the most significant one, so:
1/1x50% (maximum is now 100%) +
1/2x50% +
1/4x50% +
1/8x50% (etc etc etc) =
--------------
93.75% and you can never reach 100%
Typically though it would look like: 1/1*30% + 1/2*20% + 1/4*17% + 1/8*15% = 46.125% (where the potential max is 60% in this case). Of course the game would have to be scaled around this so that it matches, but this "need to 100" (and even beyond) is damaging the game :/ In all my years in dice games, I have never ever had a maximized skill. Wth happened?