Yahoo is launching a next-generation social network called "Mosh." It's reported that this social network can only be accessed through Yahoo's internal network, and there isn't much more information available at the moment.
However, it can be seen from the signs that both Google (as a reference) and Yahoo are beginning to take social networking seriously, that social networks may become the next market for IT companies to compete over. The rising star Facebook and the current king of social networks, MySpace, will surely also be prepared for this battle.