Ellen DeGeneres, middle, with the help of Bradley Cooper, front, took this “selfie” portrait with some of the actors and actresses at the Oscars on Sunday at the Dolby Theatre in Los Angeles.

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 on 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.

No social media moment was bigger than when host DeGeneres briefly caused Twitter to crash after going into the audience and asking Bradley Cooper to take a picture with several other stars crowding around. Besides Cooper and DeGeneres, Meryl Streep, Jennifer Lawrence, Kevin Spacey, Julia Roberts, Angelina Jolie and Brad Pitt also crowded into the frame. She asked viewers to help her set a retweet record, and they quickly complied.

By Monday afternoon, it had been retweeted some 2.8 million times, shattering the previous record of 810,000 retweets.