Dragging brakes is a decidedly bad thing.
I can see from a performance standpoint, where it may seem like you should be always on the throttle or the brake, however in practice this theory does not work.
It wont take long before the pads and discs heat up, hot enough to begin melting plastic parts and eventually bind..
Infact it took R. Cav about 11 minutes during the worlds main for this exact situation to pan out. Its a whole different sort of idea on a free spinning electric motor. While some could argue that the performance gains would be beneficial (though being smooth will do a lot more for your lap times than throttle-brake-throttle-brake) nitro cars are simply not set up for this.
I do wonder how this will pan out in 1:8th brushless, where the resistance is again on an electric motor.. time will tell.