Re Twitter:

“I agree that Twitter is on track to become an indispensable service. In April I said, “Twitter is becoming an Internet utility,” and meant it. Twitter is still a relatively small service, but users are averaging at least 15 twitter messages per day, meaning they are highly engaged. If they can get the platform stable, I believe they will eventually become as ubiquitous as email, instant messaging, sms and other forms of communication.”