What it could have been: That’s surprisingly tough to say! It combined elements of e-mail, instant messaging, photo sharing services, and groupware, without being much like anything else the world has ever seen.
Still extant? Not really. You can get into Waves you’ve created, but in August of last year–just two and a half months after Wave opened to the public–Google said it was giving up on the idea.
What went wrong? If you liked Wave, you probably feel that Google lost interest at a bizarrely early stage in its life. If you don’t like Wave, you may think that it was just way too convoluted. Or you might be like me and think both of those statements are true.
Random trivia: Google open-sourced the Wave technologies and handed them over to the Apache Foundation, which used them as the basis for Wave in a Box.