..if you take it to the dealer, that is. Since working and washing cars at BMW, I've only encountered a handful of people that said to not wash their cars. I can see them not wanting us to hand-wash their cars since dealers are known for doing more damage than good. Whenever I did anything wash-wise at work, I only used the degreaser and wheel brightener and hosed off. I never touched it with a mit.
We just got a new car wash about a week ago that we just started using. Apparently its one of the automatic car washes that BMW has even approved for washing cars. I took a brand new x6 though it last Thursday, and a newer 135i through it today and I felt nervous (though I did take mine through it to test it)