It's not a blog nor a paper, nor a very limited input field (twitter, I'm looking at you). It's the best place where I can structure the mess I've in my head.
For me, it's a place where ideas can fly by along with introspections, explanations, etc. In other words, it's the place where I can print thoughts without limits. I don't have to cut them nor make them long. The thoughts I put in thoughtstream are what they are and as they are.
The fact that it is possible to group those thoughts by logical context, allow people to read them, share them and even "discuss" them is exactly what a person with much to say and share needs.