Nokia-Microsoft announcement of the Lumia 920. On the lockscreen during the announcement were the standard lockscreen notification icons that we've come to expect, like missed calls, messages, and mail. But, there were also two new icons that weren't mentioned: Facebook and Twitter.
Integration with Facebook and Twitter are nothing new for Windows Phone, as both have been folded into the system and especially the People app, but notifications on the lockscreen are something new for the social networks. Apparently, Windows Phone 8 also has a new API which will allow other 3rd party apps to display notifications on the lockscreen, with room for up to 5 different app notifications.