Surgeon General Vivek H. Murthy recommended putting a warning on social media for minors last week, while governors from coast to coast have pushed for restrictions on teen phone use. But how worried should we really be, and what is there to do about it? Post columnists Amanda Ripley, Molly Roberts and Theodore Johnson talk through the dumbphone trend, how explicit lyric warnings on CDs backfired and what actually worked in the campaigns to stop kids from smoking.