A decade ago, when Twitter — then a scrappy, young microblogging service — burst into the mainstream, it felt like a tool for challenging authority.
Pro-democracy activists in Libya and Egypt used Twitter to help topple dictatorships. Americans used it to occupy Wall Street. And in 2013, after George Zimmerman was acquitted of killing an unarmed Black teenager named Trayvon Martin, #BlackLivesMatter took root on Twitter.