What's weird to me is Twitter trying to usurp commonly understood email nomenclature and it's messing with my head.
Quoting from the help (http://help.twitter.com/portal)
What are @Replies?
An @reply is a public message sent from one person to another, distinguished from normal updates by the @username prefix. If a message begins with @username, we collect it as a reply. Reply publicly to any update on Twitter by using the @username format.
So someone from Twitter talking to me on Facebook will address me at @ellen. Now I speak email and internet nomenclature pretty well, so to me, the name comes BEFORE the @ and the domain comes after. @ellen means you're turning me into a domain name and it's jarring every single time. There are so many other design approaches they could have taken. Mucking with the well understood @ symbol, smacks of laziness to me especially since a # or a $ or % or & or <> or + heck even a ~ or -- would have worked fine.
I'm not a domain name.