There was some discussion on this last year on another board:

http://autopia-carport.com/forum/showthread.php3?threadid=2558&highlight=clouding+on+mercedes

http://autopia-carport.com/forum/showthread.php3?threadid=3432&highlight=polymer+clouding

http://autopia-carport.com/forum/showthread.php3?threadid=4358&highlight=polymer+clouding

Personally, I've never seen it. I've used Klasse on my White 01 E320 wagon as well as my wife's Black opal E320. I've been wanting to try Blitz on top of Klasse on my wifes car. It would be a waste on my white car.