Twitter gives you a view into what anyone and everyone is talking about, the ability to easily build a following, and immediacy.
I believe Twitter is a tool that leads to other forms of social sharing. I consider Twitter a place to lay the groundwork where other people pick up things.
Twitter is a seeding medium and a place to build engagement and interaction. It is not a broadcast medium (although can be used that way at times).
It is not about the quantity of people listening at once, but the ability to lay it out there for those whose attention is drawn to what you have to say at any given moment.