I agree that the @ at the beginning or the @ in the middle is a problem.

here is my opinion Jack if you are reading.

Every tweet needs some extra field when you are creating them.

  * to: field like email. A list of people or "everybody"
  * body: 140 characters.
  * tags: relevant tags so that your tween can be found by non followers interested in a specific topic. 
  * url: seperate url so as not to use up your 140 chars. Nobody wants to use a link shortener.