Chris Taylor at Mashable notes that Game of Thrones is now HBO's most popular show:

4.4 million viewers tuned in to the Season 3 premiere episode, which is up 13% over the Season 2 opener, and even up 200,000 viewers over the blockbuster season finale. That puts Game of Thrones on a course to overtake True Blood as HBO's most popular show. If you factor in international distribution and DVD sales, it's already there.

The 4.4 million figure, of course, doesn't count those viewers who illegally downloaded the show. Thrones is the most popular TV show on the BitTorrent network. HBO's CEO and the show's producers are at pains to point out that most of the illegal downloads are coming from abroad. In particular, they point the finger at Australia, where broadcasters delay the show for months...

HBO estimates that counting all forms of viewership, 12 million people watch the Westeros-based fantasy show. "We think that number is going to increase this year, and may become the most watched show in our history," CEO Richard Plepler told us at the event.

HBO has approved a fourth season, which means the show will at least complete its adaptation of Storm of Swords, the third (and some would say best) book in Martin's Song of Ice and Fire series.

This puts Game of Thrones on par with The Walking Dead and Mad Men as the most watched shows on television for the 18-49 demo.