Google Wave

http://wave.google.com/

'a new tool for communication and collaboration on the web'

being slated as a project 'which seeks to overthrow email as the dominant mode of internet communication and replace it with a new hybrid'

http://www.theage.com.au/news/technology/web/look-out-outlook-googles-wave-is-coming/2009/05/29/1243456712775.html

not sure about everyone else, but for my money, the simplicity, ubiquity and accessibility of email will take some beating

sure, the world is becoming more 'always connected', but not needing to be connected and the asynchronous nature of email are two of the significant attributes of email

http://www.supermemo.com/articles/e-mail.htm