Coming from Foursquare, a feature that was important to me was the ability to save venues and events to a list for future reference, being able to access it at anytime (and view on the map), and share amongst others.
Since Live is built around the map, that creates a lot of interesting use cases and interaction patterns. In a map that's already saturated with information, how do we add an extra layer on top to indicate it's part of a list? What information do we prioritize in listviews? How are these items easily accessible from the home screen?
A couple of my favorite patterns were the messaging dropdown for saving something (and the ability to add a quick note if desired), and also the treatment for no results on a current mapview (I took inspiration from video game HUDs and added pointer arrows the user could tap on to take them to their destination).