I recently read a near-future sci-fi story (linked somewhere on here, I think) about an AI breaking out of its contained environment and taking over the world before we could figure out what happened and stop it (took a couple weeks, IIRC).

The TL;DR is that once it had enough compromised machines to run social media botnets, it was all over. It could use those to confound efforts to coordinate and compare data, to misdirect huge numbers of people and cause all kinds of chaos, and to smear opponents before they could get their message out (fakes or actual stolen information—it hardly mattered, all it needed to do was neutralize certain people for a few days). The story contrived to have a secret project that was able to try to resist it after that (spoiler: didn't help) but otherwise the social media botnets were enough for it to buy several days in which no-one was able to effectively work against it.