There are related terms in the current Terms of Use, namely that you may not edit "With the intent to deceive, posting content that is false or inaccurate" and that also disallowed is "Attempting to impersonate another user or individual, misrepresenting your affiliation with any individual or entity, or using the username of another user with the intent to deceive;"[1]
So in other words, deliberate falsehoods or manipulation by PR people or paid agents that hide their affiliation with a company is already a ToU violation.