I'm not sure if I get to say that I'm young enough to remember the first time, or old enough to remember the first time, that I heard the term "killer app". One thing is clear, email has been that app. It's used for formal and informal communication every single day by hundreds of millions of people. It will be interesting to see if Facebook can change the way it is used.
Paul Sakuma / AP
Facebook CEO Mark Zuckerberg talks about the new email service at an announcement in San Francisco, Nov. 15, 2010.
Mark Zuckerberg announced on Monday a new electronic communication that combines email, live chat and texting. NBC's Brian Williams reports.