Is an intake fan necessary?

What about having both a passive air intake and a fan blown air intake in the same room? If the room has a 400 cfm inline exhaust out a window, a 100 cfm intake fan, and additional passive air intake hole, would there be any issues? I haven't found any answers about this yet. Also, should the 2 intake methods be on opposite sides of the room? With the exhaust above and in the center I could see it providing great circulation.

... why would you want that really?

And real quick, im running passive exhaust, a vent grate with carbon filter on one side (Help prevent light/smell leak) and a 265cfm exhaust. When my room is sealed, and the fan is on, it sucks the visqueen walls in about a good inch or so. Fairly large ammount of neg air pressure... can that be bad? Is it really possible to have... to much neg air?