I think looking at it this way is a bit naive. While I agree that "attachments" shouldn't take up tweet text, the 140 character limit is a core component of the service. Call it a micro blog or a mass SMS, Twitter is 140 characters.

That said, I think most comments are missing the point - having attachments not take up characters really won't make the service any more useful to the mainstream... That's the real problem in my opinion.