Google Wave is their new product aimed squarely at the recent surge in social sites and also at communications. At its best, it could be a new paradigm of communication tools allowing real time communication, collaboration, and sharing. On the other hand, it might be an attack on social media sites and their concentration of power and reach.
While e-mail and even instant messaging are similar in basic operation to plain paper mail, Google Wave could start to branch out into capabilities and functionalities beyond that. The popularity of tools like IM, SMS, and Twitter show that people crave a quick, real-time platform to communicate. But aside from social communications, many practical uses would require documents for collaboration and group effort which are awkward with these traditional methods of communication.
Wave provides an integrated metaphor to handle these traditional methods while adding additional functionality and automation. In addition to having lightweight apps and widgets, Wave allows "robots" that can interact with the wave in predetermined ways. Robots can provide additional content by referencing existing content or pulling from other services for integration.
The other aspect of Wave is that it is going to be open sourced and distributed. This could be a way to build interoperating systems that would vie with the existing social media giants such as FaceBook and Twitter. Being based on Jabber's open XMPP protocol and with Google's promise to open source the project, Wave servers could spring up across the Internet working together and tearing down the walled gardens that tend to concentrate users in a few closed systems.
If Google Wave works as advertised, it could allow users to communicate and collaborate with their own self-determined identities without locking that content and communication on a proprietary system. A successful Wave could end the domination of closed systems that tend to hold the content and relationships hostage. This would be bad for FaceBook and Twitter, not to mention MySpace (who mentions them anymore anyway).
Official Google Blog: Went Walkabout. Brought back Google Wave.