Stuart J. Russell (he of the AI textbook) claims in Human Compatible that YouTube is already an example of a runaway feedback loop between AI (YouTube's recommender "algorithm") and humanity (viewers, content producers, YouTube staff, and society at large). The AI doesn't have a body, a voice, a conscience, or a purpose yet it is busily working away to maximize engagement by changing people's minds, and in particular by bringing extremism into mainstream discourse.

(It seems to me that framing it this way does seem to absolve YouTube executives of responsibility by making the AI, not them, seem like the agent.)