There were 800 million social media interactions around TV shows on the day they aired in the US in 2012

"The second annual Year End Stats Report from Trendrr includes data tracked via Twitter, public pages on Facebook and applications such as Get Glue and Viggle. For the year (period covers through November), Trendrr measured more than 800 million social interactions around TV programs on their day of air; taking into consideration all the chatter surrounding programs when off air, that number would reach into the billions, the social TV analytics company said.
An early look at the data reveals August as the most interactive month -- thanks to 17 days of the Summer Olympics on the networks of NBC -- but every month of 2012 drew at least double the number of social interactions than the same month in 2011.
Overall, the year saw a huge 800% growth of social TV chatter on Twitter, and it more than doubled on Facebook and in Apps.
For a second straight year, Nickelodeon's "SpongeBob SquarePants" was the entertainment program with the most social activity, accounting for nearly 25 million social interactions. Also high on the list were Fox's "The X Factor" (about 17 million), NBC's "The Voice" (11.5 million), USA's "WWE Raw" (11 million) and ABC Family's "Pretty Little Liars" (10.5 million), which holds the record for a single episode (1.52 million interactions for its mid-season finale)."

Source:  Data from Trendrr, reported by Variety, 26th December 2012

See the original Trendrr Infographic here

Note - I'm assuming that this is US only, given that no UK shows (or Japanese shows, or Brazillian shows...) appear in the figures