1. Twitter in its native form assumes we're ok with not keeping up with the abundance. Tweets are going to scroll by when you're not looking, and you're never going to see them. Twitter assumes you will let them go, the way most of us cannot leave messages in our email inboxes unread (or undismissed).

2. Social asymmetry addresses the scaling problem. At Twitter, the people you follow are not necessarily the people who are following you. That's exactly not how mailing lists and weekly status meetings work, and Twitter's approach impedes the back-and-forth development of ideas. But, maybe that's not what Twitter is primarily about. And the asymmetry means that some people can have lots of followers but still participate as listeners.