The most prominent rating service, Nielsen Media Research, offers a list of the in the U.S., gathering data from a statistical sample of U.S. homes. The Nielsen ratings are widely used among television networks as the definitive guide to what shows are popular. They also influence advertising rates.

"We have all kinds of data points on popularity now that are divergent from what Nielsen would say the top shows are in America," Tanner said. The most popular show pages on the TVGuide.com site rarely correspond with Nielsen's top-rated shows. For instance, the most popular pages on TVGuide.com are "Criminal Minds" and "The Vampire Diaries," neither of which are strong showers on the Nielsen ratings.

"I can't say what I make of it, but it is a fascinating set of data," she said.

Whatever the merits of social media for the television industry, the networks consider it a necessity. Within the past few years almost every network has set up an office of some sort for social media, Tanner said.

She noted that in August 2010, TVGuide.com asked 10,000 of its users if they updated their Facebook status while watching television. About three-quarters said they did, up from 39 percent a year ago. "It shows a big shift in behavior," Tanner said.