After playing Call of Duty: World at War for a few minutes I ran slap bang into an invisible wall.  I don't know if it's just me but I feel invisible walls are a sign of bad level design.  You could get away with it in the days of old because of the severe limitations with game engines but nowadays there's nothing really stopping a level designer putting in a cliff face or an impassable river, anything other than an invisible wall.
I'm running through a deep jungle and then I hit an invisible wall, talk about take you out of the experience, game developers should ban the use of them.

What's everybody elses thoughts?