QUOTE
The reason for the ban is likely to be that the BMW websites have been caught employing a technique used by black-hat search engine optimizers: doorway pages. As you may know, a doorway page is stuffed full of keywords that the site feels a need to be optimized for; however, as opposed to real pages, this doorway is only displayed to the Googlebot.
It's nice to see that even Bavarian big boys are not too big to get their wrists slapped.
Source: Google Blogs