Just a quick note to archive the way Google Buzz is using the @ syntax. From “Google Buzz Tips":
If you’d like to send a private message to someone, type @ and use Gmail’s autocomplete feature to find the email address of your contact.
In practice, you address other users by typing an @ symbol followed by their e-mail address, like @firstname.lastname@example.org. This is exactly what I proposed a while ago as an easy way to address any user on any Web application:
Afterthought question: can this microsyntax be expanded to @user@application so that we can finally address any user on any Web application easily. I’m thinking about that.
For now, you can only send messages to other Google Buzz users but I’d expect this syntax to be used to address users of other supported destinations (twitter et al).