1. Promoting stocks that are not the subject of the board. 2. Repetitious posting of identical or nearly identical text.
I do not believe that on-topic posting about facts or one's opinion of a specific investment is spam unless it the same text post over and over again. For example if someone reposted the same PR or exact same wording of a post every day.
I think that when you include ambiguous terms like "excessive" you then need to define excessive. Also, who is to say if a post added value to a discussion or not? What is the definition of adding value?