A tipster tells us Google has backed out of talks to buy Digg, the popular news-discussion site fronted by Kevin Rose, the Web-video personality and San Francisco Casanova. There have been hints all week that Google has been cooling on Digg. Marissa Mayer, Google's reigning princess of pageviews, had once fancied Digg as a means of improving Google News, one of her Web properties. Last month, at her behest, acquisition talks were getting serious. But then Mayer brashly (and perhaps foolishly) announced Wednesday that Google News generated $100 million a year in revenues for Google. Translation: Who needs Digg?Shortly thereafter, reearsh firm Hitwise ran numbers which showed that Digg would be inconsequential for Google's traffic, only the 13th largest Web property, well behind Google News. Coincidence? Perhaps, but they can't have been helpful for Digg's negotiations. One other sign that the deal has been going nowhere: Digg has been interviewing for a head of PR. That's a position they wouldn't fill if they were close to a sale. That said, we hear Digg board member Brett Bullington, who helped sell JotSpot to Google in 2006, has been pushing to keep negotiations alive. So are things on? Are they off? Never say never in deals. But even Digg CEO Jay Adelson acknowledged this week, at a meetup with Digg users in Chicago, that his company has been too prone to leaks during negotiations. Could he be getting a taste of the same from the Google side? That's a theory I dig.