I didn't believe the Fortune 500 mortality statistics in TheLivingCompany so I grabbed the public data from Aggdata's public 1955-2008 repo. Having run through the top 100 (alphabetically, so probably bias as corporate names probably follow fads), I put the data up at mortality.xls.
It seems unlikely that De Geus means Bankruptcy, Dissolution, or Acquisition when he says dead. He indicates sub-30 year mortality age and I'm seeing 70-year age at death with 20% mortality (Granted this could swing...). It seems likely that De Geus means "No Longer in Fortune 500". That seems problematic as the company would have to be in a market that scales with (capital, people, technology) in order just to keep pace. Most companies seem to make their niche and stay in it.