I havent really heard much about this but it is something I have thought about myself... i may have even posed the question on here before. Its like, if you know that you are dreaming, does it somehow interfere with the subconscious symbolism that would normally present itself in dreams? I've also noticed that sometimes when I become lucid, eventually the scenery starts to 'fade away', because I consciously realize that its just a dream. I'm sure this can be overcome but I'm still working on it. Interesting things to think about.