I used twitter quite a bit for a couple years, tried to be a good "pro user" that gets tons of value from the service by painstakingly curated my own feed, and eventually left because it was all too much. I'm interested in news, have little interest in my friends (on twitter that is; I like my friends more in real life) and zero interest in celebrities. If that makes me a "casual", oh well! Moments seems like a fantastic product to me, and might bring me back as a user.