As I turned on my Xbox this morning something interesting caught my eye, in the spotlight section there was an Inside Xbox video about Left 4 Dead 2. I normally don't pay attention to these type of things but since I am looking forward to Left 4 Dead 2 I decided to give it a look. It features a small interview with Gabe Newell Chet Faliszek and Robin Walker as except for the parts where it shows the respective people the interview plays over footage of the leaked trailer along with some footage of the New Scavenge Mode.
Near the end Robin Walker comes on and announces the details of realism mode. He said that everything that helped you play with a group of strangers is now gone. Including showing you there silhouette if there is a wall blocking your view, telling you when they are in distress, and highlighting useful items. Among those things he also said a few smaller things would be changing such as zombies have more health, they are more immune to body damage so aim for the head, and that witches would be instant death not just incapacitation.
Sorry if this has already been announced I haven't seen it anywhere.