The Hive by Barry Lyga
In a futuristic America, social media is held in check by the Hive that draws mobs together to mete out real-life justice for people's online actions--and it's legal. High school senior Cassie Mckinney believes in the Hive until grief over her father's death makes her post an edgy joke online that goes viral and the Hive turns on her. Cassie goes on the run and becomes part of a group of Hive outcasts who show her the truth behind the Hive.
Review from School Library Journal:
Who better to police public behavior than the public themselves? Individual posts and actions can be Liked, Disliked, and Condemned, and Hive Justice is swift and inventive. When a snarky comment goes viral, Cassie McKinney finds herself at Level 6: the Hive Mob can kill on sight. Cassie, an expert hacker, goes on the run, stumbling across other renegades, but she's not sure whom she can trust. Peppered with coding lingo and hashtag commentary, the novel reads like a movie waiting to happen, with breathless, nonstop action; rooftop chases; and an attractive, diverse group of characters. Authors Lyga and Baden, working from a concept from actor Jennifer Beals and producer Tom Jacobson, take current social media ideas to the next level, with a population comfortable with camera everywhere, a governmental mandate to be connected, and Blinq, an all-encompassing platform.