See Who's Editing Wikipedia - Diebold, the CIA, a Campaign

On November 17th, 2005, an anonymous Wikipedia user deleted 15 paragraphs from an article on e-voting machine-vendor Diebold, excising an entire section critical of the company's machines. While anonymous, such changes typically leave behind digital fingerprints offering hints about the contributor, such as the location of the computer used to make the edits.

In this case, the changes came from an IP address reserved for the corporate offices of Diebold itself. And it is far from an isolated case. A new data-mining service launched Monday traces millions of Wikipedia entries to their corporate sources, and for the first time puts comprehensive data behind longstanding suspicions of manipulation, which until now have surfaced only piecemeal in investigations of specific allegations.