Here's our roundup of the top digital and social media stories you should know about (and from Andrew Beaujon, 10 media stories to start your day, and from Kristen Hare, a world roundup):

— What makes a tweet likely to be retweeted? An algorithm developed at Cornell thinks it knows, and you can test your predictive powers against it in an interactive quiz at The New York Times by Mike Bostock, Josh Katz and Nilkanth Patel.

— According to eMarketer, revenue from smartphone and tablet ads will surpass revenue from radio, magazine and newspaper ads for the first time this year, Robert Hof writes at Forbes. Mobile will still trail television and desktop/laptop ad revenue, though.

— Mashable's Brian Ries has a roundup of fascinating Twitter data from yesterday's U.S.-Belgium World Cup match.

— SCOTUSblog got 20,000 new Twitter followers on Monday after engaging with users who thought the Supreme Court blog's account was an official Supreme Court account. American Journalism Review's Cory Blair has a Q&A with SCOTUSblog publisher Tom Goldstein.

— Facebook did its icky emotion-manipulation study for the benefit of you, the customer, Megan Garber of The Atlantic reports from the Aspen Ideas Festival. Said Monika Bickert, head of global policy management: "Most of the research that is done on Facebook—if you walk around campus and you listen to the engineers talking—is all about ... 'How do we better suit the needs of the population using this product, and how do we show them more of what they want to see, and less of what they don't want to see?'"

— Gawker editor-in-chief Max Read wants internal staff chats to be less of a "time waste," so he's making them public. Caroline O’Donovan explores Gawker's new Disputations vertical at Nieman Lab.