There is some new information, albeit from unnamed sources, on why Chris Bangle left BMW. Apparently he had disagreements with the BMW board and his successor von Hooydonk on the future direction of Project i, which is expected to spawn the spiritual successor to the BMW Isetta.
It seems that the board wanted one way and Bangle wanted another, so he decided to resign because as Head of BMW Group Design he could not take responsibility for a design strategy he did not agree with, or rather did not choose. BMW still wanted him though, and offered him other jobs such as design director of the US-bsaed DesignworksUSA, a company which von Hooydonk previously headed.
Bangle revealed later that he will be starting his own design house, but maintains he will not just be plastering the Bangle name over any industrial design product. Macbook Pros will flame surfacing or a toaster with a Bangle Butt anyone?