so i played Knack last night, game+ and i think something is up with the game, as 4 chests i opened had nothing from other users, including most of you guys. and these were the obvious chests. So i don't think the game gives you access to every chest your friends opened. I then tested this by starting a "hard" mode game and went to the same chests, there were about 12 other people from my friends list on the pick list of items from those same chests which has nothing from anyone 20 minutes prior. So i think the game randomly chooses if it gives you a friends pick or all of your friends based on difficulty level you have picked to play on.
Just thought i'd share this tidbit of info