Good points but our definitions of twitter spam are different. I don't consider boring/dumb tweets from people I am following as spam because I am following them. Twitter spam to me are all the accounts setup by people who then start following as many people as they can, which sends notifications, leading me to click on their profile and see who they are and if I want to follow them back. That is Twitter spam. What you are talking about is just junk tweets that people need to decide for themselves if the quality vs quantity is worth continuing to follow someone.