It has been revealed that Facebook embarked on a smear campaign against rival Google.
The details came to light when one blogger approached by PR firm Burson-Marsteller published the e-mail exchange.
Burson had been touting stories on behalf of an unnamed client about the Google service Social Circle.
Blogger Chris Soghain did not want to pursue the story and later released the e-mails he had exchanged with Burson.
When the e-mails were published there was a mass of rumours about who the client could be, with Microsoft and Apple in the frame.