@Budnitz - Just had a random idea. Twitter's biggest issue as an asynchronous network has always been the "Okay, I signed up... Now what? Why isn't anyone talking to me?" problem.
What if you randomly provided a message to consistent users called "Say Ello".
"So-and-so just signed up. Why not send them a note to make them feel welcome?"
Would instantly make this place feel more friendly and conversational than other networks, and help solve that "now what?" problem.
Might be a dumb idea, but it would impress me as a convert from anywhere else.