It had been speculated for a little while, but Sony just made it official: a big part of the PlayStation 4 will be a "share" button. It plays a big part not just on the dash and in your games, but in the way your friends lists are managed as well.
Your friends list can be expanded to include accounts from third-party services like Facebook, including real-world names and profile images. You can record and share videos and screenshots, including streaming your content live. You can access the PS4's online services not just from your PS4, but from phones and tablets as well, queuing up downloads and messaging friends.
Much of this is handled via a "share" button right on the front of the control pad. You can see an example of the PS4's user interface above and below.