Where do you mostly spend your time in on the web? If you think it might be some social site it isn’t. Chances are that you mostly spend more time on your email more than anything.
It has come to Google and Yahoo! attention that they should spend time on social networks. Google and Yahoo! already have a lot of the stuff that Facebook and other social networks have. So why not just make it a social network?
Yahoo! plans to create an inbox 2.0. This version of the inbox automatically determines how often the relationship is between the person who is emailing and instant messaging. It will sense how often you interact with the other person and will put it as a more important message than the others waiting for you.
Source: http://www.smartbiz.com/article/view/2323/1/58
