Waver is described as 'Google Wave is a great way to communicate and collaborate' and is an app in the Office & Productivity category. There are three alternatives to Waver for Online / Web-based, SaaS, Android, Chrome OS and iPhone. The best alternative is Moo.do, which is free. Other great apps like Waver are Rizzoma (Free, Open Source) and kune (Free, Open Source).
Email and IM are linear contextless communication tools. Messages pile up and get lost or become redundant. There's no way to keep track of who replied to what, or which version of the conversation is the newest.