After using it for just a few days, I think the biggest innovation that Buzz has brought is integration into the inbox which has driven significant adoption. The second biggest innovation is the support for open standards. All my communication systems are now linked. Twitter, Facebook, LinkedIn, Posterous and Tumblr, Chat, Google Reader, Gmail for the most part communicate with other effectively.
The next big question in my mind, is how valuable is data ownership? If my data can be syndicated effortlessly or near effortlessly across services, then the data is a commodity. The relationship and time with the user is now the scarce (and therefore the more valuable) resource. Given equal access to data, the types of analysis that services can provide is relatively undifferentiated. Rather the interface must provide differentiated value.
Reflecting on other communication mechanisms, monetization at scale has mostly been achieved at the interface closest to the user. Telcos have billing relationships with customers; social networks have login relationships which is the way MySpace made hundreds of millions of dollars.
The counter argument to this is that communication systems have historically not been able to generate significant revenues: AIM and email are great examples. But if you believe for a moment that these communication systems will give rise to significant revenue streams, then the revenues will aggregate to the service providers who provide the best interfaces into commodity data.
Google, Facebook and Twitter all have significant presence and session times with users. But Twitter has a wrinkle: the app ecosystem is an abstraction layer separating the user from Twitter and providing the best user interfaces has significant value for users. To prove my point, note the success of TweetDeck as a paid app in the iTunes store.