You've heard the adage that a picture is worth a thousand words, but when that picture is protected by copyright, the picture is only worth three words: cease and desist. OK, that's kind of a lawyer joke. But it illustrates how protective people are about finding their images used online without permission.
The myth about social media in the classroom is that if you use it, kids will be Tweeting, Facebooking and Snapchatting while you're trying to teach. We still have to focus on the task at hand. Don't mistake social media for socializing.