The chat ads sort to by post activity to show the last 8 active users: users = users.sort(function (u1, u2) { return u2.lastPost.raw - u1.lastPost.raw; });
Some users haven't posted anything in the room they're in, so this there's a NPE accessing .raw. This causes that room not to show up in the ads (if it was one of the two that was going to show up).
