From http://www.economist.com/finance/displaystory.cfm?story_id=12523898:
After languishing below €200 last year, it [VW's share price] jumped to more than €1,005 at one point on October 28th, briefly making VW the world’s most valuable company. Porsche may have made paper gains of €30 billion-40 billion in what one analyst described as “one of the most brilliantly conceived wealth transfers ever.”
The greatest damage is to the reputation of Germany’s capital markets, where regulators are now belatedly investigating what went on. Allowing acquirers to build large secret stakes in bid targets does nothing for confidence.