Twitter is in an interesting place. As a one to many broadcast medium, they have many people who are using it commercially, people like me who would be willing to pay a fee. Really, twitter charging me $5-$10/month or so is not going to register much more than twitter being free, at this point.

What they have to be careful of is that if they start charging the non-commercial users, those users will go elsewhere. And if those users go elsewhere, the commercial users will also go elsewhere.

So, if they can figure out how to charge me without charging my customers, they are golden. How to do that? I have no idea.