As the SharePoint 2010 social features are limited, either custom code or a 3rd party add-on is necessary. Here a nice post about Extending SharePoint 2010 Social Features with custom code.
Category: Blogs
MVP Yaroslav Pentsarskyy shows how to customize the SharePoint blog template and use it in a more microblogging similar manner.
http://sharepoint.microsoft.com/Blogs/GetThePoint/Lists/Posts/Post.aspx?ID=438
Thomas Maeder | thomasmaeder.com 