As announced in November 2011, Google Wave is being shut down completely as of Monday, April 30. All Waves will be deleted as part of the shutdown.
Navigating to google.com/wave now takes users to a Google Help page describing the shutdown.
The online real-time collaborative editing tool was made read-only as of January 31, 2012. The service initially debuted in September 2009 in a limited preview release to 100,000 users, who were allowed to invite additional users in a system similar to Gmail's initial rollout. Google Wave was released to the general public on May 19, 2010. Less than three months later, on August 4, 2010, Google announced that it would suspend development of Wave, but would maintain the service for at least the remainder of the year.
While the service was an interesting merger of multiple features from various communication methods, such as email, instant messaging and wikis, a lack of interest was cited as the reason for Google Wave's demise. Many users might have found the service confusing and perhaps not a very intuitive fit for their uses.
For those that are interested in continuing to use a service like Google Wave, the service lives on at the Apache Software Foundation, where development of Wave has continued since 2010. Their efforts can be seen at Wave In A Box.