From Social Patterns
A user wants to see where they are (or their stuff is) in relation to other people and places.
Use this pattern to automatically place people, status updates, photos and other objects on a map.
Automatically place the item on a map.
If the item has an address associated with it, like a business, automatically place the item on a map.
Allow the user to associate an address with an object.
Consider allowing users to drag and drop items (photos, listings, friends) onto a map and associating a location with the item.
Present the item location to the user with a graphic pointer on the map.
Convert the map location to geo:lat and geo:long tags in the item’s associated tag set.
Providing easy, drag and drop tools for placing items on a map can offer alternative ways to filter objects on a site. Additionally, showing items on a map can provide locally contextually relevant information and can help support local, face-to-face meetings and gatherings between people.