I agree that the more people join steemit, the easier it will become to exchange value between members/users, especially without going through - as you said - centralize exchange. However, and I don't know if this will make sense to everyone, I feel that the more people join steemit, the greater the possibility of it losing its distinctive characteristics. A billion people are great, but the platform might no longer be a place to come for valuable content, engaging discussions or simply an escape from all the other futile social media platforms out there. This is my only apprehension!