NEW YORK — Ellen DeGeneres’ celeb-studded selfie from the most-watched Oscars telecast in a decade was a landmark social media moment at a time online conversation is boosting television viewership and vice versa.

It’s also a murky example of what is or isn’t product placement in a hyper-marketed world. Would the world’s most retweeted photo have been shot by an iPhone if Samsung hadn’t been a commercial sponsor of the Academy Awards?

An estimated 43 million people watched “12 Years a Slave” win the Oscar for best picture Sunday night. It was the most-watched Academy Awards since 2004, when “Lord of the Rings: Return of the King” was the best picture. And it was the most popular entertainment event on TV since the “Friends” finale that year. The Oscars are generally the most-watched TV event of the year after the Super Bowl.

Oscar night was also big for Jimmy Kimmel. The ABC late-night star drew just under 7 million viewers for his post-Oscars special, the biggest audience he’s ever gotten on ABC, despite starting at 12:42 a.m. on the East Coast.

The ratings provide further evidence of how big event programming is a growth engine for broadcast networks, in large part because of fans watching the event and conversing with friends on tablets and smartphones. Twitter said that some 14.7 million tweets mentioning the Oscars or prominent actors and films were sent out during the telecast.