That's coincidence, though. I used Twitter to keep in touch with friends via SMS in 02008, and the messages had space for a prelude to say who they were from.

That's coincidence, though. I used Twitter to keep in touch with friends via SMS in 02008, and the messages had space for a prelude to say who they were from. In the opposite direction, you could use that space to tell Twitter to send the message privately to someone.