I still think they should try and kill some of them. If anything the fallen zombies would create an additional buffer between the active zombies and the wall. I mean I know there are probably like 10,000 of them there, but heck, 100 here--100 there adds up. Rocks or bricks from the top of the wall would be pretty effective I would guess.
I liked the episode, but the one thing my wife and I found funny was
Rick gives the big speech about they need to be quiet and cover the windows, yet it seemed there were a bunch of scenes last night where people are just having a conversation next to the wall.
Oh and the Carl slap fight was just awesome!!