It might sound stupid but some of my friends are going to miss google buzz a big time. In fact most of us met only on Google buzz, we dont know each other on facebook, FB is banned inside our organizations.
Our group grew very large eventually we held buzz group meets and a 25+ treks to western ghats in India. The common interest we share is an Indian language called "Marathi".
Now that google has closed Buzz we want an open source alternative which I will install on my private server and let everyone access. The closest thing was Jaiku (Ironical given it is another google product which got killed) but it's interface sucks a big time.
It's open source: http://status.net/open-source