Twitter Clones and their Place?

Twitter is a phenomenon that keeps growing in popularity.  With new developers creating  tools to integrate with it, Twitter keeps getting new features everyday and extra data portability functionality…

Twitter also has many look-alikes out there. Does anyone see advantages to Twitter “clones” such as Rejaw and YouAre, and white label or self-hosted solutions ShoutEm  and Laconi.ca? Especially for academic institutions and corporate learning departments?

Any advantage at all in trying to replicate Twitter’s functionality? Any added features that you may find useful?