Now, when you are writing a status update and want to add a friend's name to something you are posting, just include the "@" symbol beforehand. As you type the name of what you would like to reference, a drop-down menu will appear that allows you to choose from your list of friends and other connections, including groups, events, applications and Pages. Soon, you'll be able to tag friends from applications as well. The "@" symbol will not be displayed in the published status update or post after you've added your tags.

This is a terrific upgrade for Facebook. I predict this will be massively popular almost immediately. If you use Twitter, you know that Twitter lives and dies by @ mentions.

Facebook is one step closer to marginalizing Twitter. Just another battle in the fight, but nonetheless I can't see both existing forever.