There is no proven correlation bettween the number of followers and $$$ earnings on Twitter. What I am noticing is that if the followers are targeted and "paying attention to you" in a particular niche, yes, money can be made. There are many variables involved with followers. For example, you can have 15,000 followers but that doesn't mean that they're all online and ready to read your tweet(s) when you send them, unles you're tweeting every 15 minutes or so. Also, there is a growing number of bloggers bitching about people using twitter for money/marketing. They want to keep it some sort of pristine "what are you doing?" social network -which is what it is - instead of a place of commerce. I don't know about you, but If I'm going to spend any significant time online tweeting, I want to see some ROI. Maybe I'm past the chit chat stuff. If you're in a targeted niche, it IS possible to make contact with key people. An example of that is if you were an actor trying to hook up with a casting agent. You could promote a video showing off your acting skills, etc.