A question from Yahoo! Answers:

How come BMW is not traded as an adr on the NYSE or Nasdaq?

Because BMW management refuses to publish accounts according to U.S. GAAP. Daimler Benz, which listed its ADRs in the U.S. long before the Chrysler merger, used to be one of the favorite study subjects in comparative accounting; their earnings computed according to U.S. GAAP would invariably be way more volatile than earnings computed according to the German Commercial Code. BMW management does not want anyone to know how volatile their earnings are…

But the title of the most opaque company, in all honesty, should go to Porsche; those guys even refuse to publish quarterly accounts, insisting that semi-annual accounts are good enough.