There were a few Bitcoin/dogecoin scams, unsurprisingly.
Two incidents I remember are a) /r/hearthstone, where a moderator who owned a fansite killed links to other fansites and b) a moderator of /r/tumblrinaction posted a link to a MLM on the top bar.
Don't forget when it was revealed that a moderator on /r/adviceanimals also owned quickmeme.com. He apparently ran bots that downvoted any non-quickmeme images and upvoted quickmeme images.
Two incidents I remember are a) /r/hearthstone, where a moderator who owned a fansite killed links to other fansites and b) a moderator of /r/tumblrinaction posted a link to a MLM on the top bar.