One aspect of social media that surprised almost everyone at first was the popularity of outrage. Users seemed to like being outraged. We're so used to this idea now that we take it for granted, but really it's pretty strange. Being outraged is not a pleasant feeling. You wouldn't expect people to seek it out. But they do. And above all, they want to share it. I happened to be running a forum from 2007 to 2014, so I can actually quantify how much they want to share it: our users were about three times more likely to upvote something if it outraged them.
Were people actually outraged less frequently before social media? "Viral" outrage was limited to spreading through in-person interactions, but there was still mass media designed to generate outrage.