E-mail has most ... of our attention .... [and] has all the elements needed for a social ecosystem, namely the address book.It probably is not fair to pick on Yahoo here. Microsoft and Google also seem to have had only limited success with their social network apps while letting their e-mail apps languish.
Yahoo might have taken the wrong approach to ... social networking ... It should have started from within Yahoo's email service, which has some 250 million subscribers.
[E-mail should be] something better, something that doesn't make us all groan every time we open our inbox.
But, I think Om has an excellent point. Rather than try to replace e-mail apps with social apps, most people might be better served by bringing more social features to our e-mail apps.
On this topic, you might be interested in checking out "Inner circle: people centered email client", a fun CHI 2005 paper out of Microsoft Research.
Update: Two months later, Saul Hansell at the NYT posts about the Yahoo Inbox 2.0 project, an extension to Yahoo Mail "that can automatically determine the strength of your relationship to someone by how often you exchange e-mail and instant messages with him or her" and displays "other information about your friends ... much like the news feed on Facebook."