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It had all the appearances of a serendipitous selfie.
But not long after the shot of Red Sox hitter David Ortiz and President Obama went viral on the Web, it was revealed to be a clever marketing ploy set in motion by the electronics giant Samsung.
And it worked. The photo that Ortiz posted on Twitter was seen by hundreds of thousands of his biggest fans, and likely millions more people elsewhere on social media.
But it also raises new questions of what is advertising on the Web and what isn’t. Is every celebrity tweet now suspect or paid for by corporations? Is every selfie an endorsement? It’s often hard to tell these days, especially as celebrities and sports stars are sending out countless tweets to legions of fans that follow their every post on the Web.