To give a totally useless answer, its not a problem until it becomes a problem! Meaning that the weir or skimmer door does serve a function, but unless the water level gets too low you are not likely to notice. The floating weir helps regulate the flow of water into the skimmer when the pump is on. When the pump is off, it closes and keeps debris in the skimmer from floating back into the pool. If you do not have a lot of falling, floating debris in your pool, then you won't be bothered by debris washing back into the pool. If the water level starts to get low, you will see more of a vortex effect sucking air into the skimmer without a weir in place.