This happened in a big way during the election -- the Clinton campaign poured millions into paid online supporters to go on reddit, etc. through an organization called Correct the Record. Once this became known every post in support of Clinton was suspect; people noticed similar comments appearing out of the woodwork, accounts which did nothing but post pro-Clinton comments. The entire politics subreddit turned into a lockstep echo chamber -- no anti-Clinton dissent of any kind allowed for a month or so before the election. Anyone who mentioned correct the record was instantly banned. I'm sure there was some amount of Record Correcting out there but the tragic part was that every single comment in support of Clinton no matter how earnest and honest and real was immediately suspect and accused of being a paid troll. It's impossible to have a real discussion when you are always wondering if the other side of the conversation is not arguing in good faith, and that's the exact climate this sort of thing creates.
