We mentioned geofencing a few times (first time in 2005!) and in the past weeks during my leave, O'Reilly shared an article about geofencing named The rise of location-triggered offers, and summarized the introduction of geofences on Flickr.
From the first O'Reilly article: "To make these location-triggered offers, merchants need to delineate a "geofence" around their retail outlets — a radius or polygonal area in which customers who have opted into a deal program can be notified on their mobiles that an offer is available nearby."
From the Flickr announcement: "Today, we’re announcing Geofences, a new feature that will help you to better manage your geo privacy settings on Flickr. Geofences are special locations that deserve their own geo privacy settings. For example, you might want to create a geofence around the your “home” or “school” that only allows “Friends and Family” to see the location of the photos you geotag in that area. So the next time you upload a photo with a geotag in the radius of a geofence, it will follow the default geo privacy you’ve designated for that hotspot."