http://www.wired.com/magazine/2009/10/ff_twitter/
Basically the article sums up how Twitter doesn’t want to be greedy and sell out to a bigger company but at the same time they still want to take control of their own company and make the changes they see fit. They envision twitter eventually making its way into cell phones as a quick text option and shortcuts in cellphone browsers to the service to better integrate twitter with the rest of the world and every portable object you have. They still want to keep the service simple however, which is why the have always tried to keep the actual service itself as simple as possible yet still allowing for an open API to developers so they can do as they please. They always envisioned geeks taking twitter and hacking it to do as they pleased.