With Twitter the phase of "do we really need it?" is over. The "how do we use it?" phase is right now. There are numerous ways of using Twitter for everything from business to bull**** and even clients come up to me and ask me about Twitter after reading
"We want to limit the length of a review in our application to 140 characters, because we may want to use SMS at some stage. That's a tiny change, right?"
Wrong.
There are no tiny changes when you're committed to delivery quality software.