Collaboratively edited information on social media that circumvents traditional media gatekeepers poses a challenge to public relations practitioners. The online encyclopedia Wikipedia gives corporate critics the opportunity to shape the public image of major corporations. This longitudinal panel study analyzed the framing of 10 Fortune 500 companies on Wikipedia between 2006 and 2010. It was found through content analyses of tonality and topics of more than 3,800 sentences in the articles for Wal-Mart, Exxon Mobil, General Motors, Ford, General Electric, Chevron, ConocoPhillips, Citigroup, AIG, and IBM that the negativity increased over time and that the focus shifted from historical information to legal concerns and scandals. The findings show that public relations practitioners need to pay close attention to the forced transparency about their companies on Wikipedia.