So far, the only thing I've seen Wave used for is chatting and discussions about what Google Wave can be used for. Lifehacker even compiled a list of the best uses for Wave. But it's apparent what Google's intentions are for this application and that is to be used for getting things done; not social networking.
Truthfully, Wave is ideal for any project that necessitates collaboration. With the capability for real-time editing and sharing of documents, it would be good for creating a wiki with multiple authors. For the field of journalism, editors and authors could work together to hash out ideas and even edit or revise articles without the lag time of e-mail. For small businesses with remote employees who need to work on a project together, Wave would take the pain out of such collaboration. All parties could log in and make edits while others watch and contribute.
Including people on a Wave simply entails dragging and dropping the contact from a contact list, and collaborators can add as may people to a Wave as necessary. Want to post to a blog or to Twitter? All you have to do is drag and drop the API information just like any other contact. This is ideal for people who want to post to multiple sites or networks without having to log in to any of them. All the work can be done in one place and the content syndicated.
As with all Google applications, Wave is connected to your Google account. This can be a double edge sword. Since Wave is designed for integrating contacts and interconnectivity, anyone you've ever e-mailed with a Google account and Wave will automatically populate your Wave contacts. The only way to remove someone from your Wave contacts is to delete them from your Gmail contacts. But if you want any amount of separation between the two, this is practically impossible.
The good news is that Wave is still in development and Google is looking for feedback. So if you have access to the preview and want to make a suggestion for the improvement of the application, Google is all ears.
In truth, much of Wave's basic functionality as a place to create and store documents that can be edited by others in real-time, was available with GoogleDocs. The main difference is that Docs was created as an internet based word processor. Those documents could be shared and edited by multiple people but Wave streamlines this process and has great potential for simplifying creative collaboration.