It's not news that attackers try to influence and skew these recommendation systems by using fake accounts to upvote, downvote, share or promote certain products or content. Users can buy services to perform such manipulation on the underground market as well as "troll farms" used in disinformation campaigns to spread fake news.
"In theory, if an adversary has knowledge about how a specific user has interacted with a system, an attack can be crafted to target that user with a recommendation such as a YouTube video, malicious app, or imposter account to follow," Andrew Patel, a researcher with the Artificial Intelligence Center of Excellence at security vendor F-Secure explained in a blog post. "As such, algorithmic manipulation can be used for a variety of purposes including disinformation, phishing scams, altering of public opinion, promotion of unwanted content, and discrediting individuals or brands. You can even pay someone to manipulate Google’s search autocomplete functionality."