The Facebook Fan Page allows administrators to geo-target each post. If you are the administrator of a fan page, specifically a large fan page, with fans from all over the United States, or even the world, you can direct a post to target fans based off of their geography.
For example, if you are hosting an event in Cancun, you may want to only share this event with locals. (After all no one from the U.S. is going to go all the way to Cancun for a single event)
1) After you post your message in the status update box, click on the drop down box next to the lock icon. Select the "Customize' Option.
2.) Next select the country you wish to target. The dialogue box will provide you with options as you begin to type. Then select the city and, if you wish, the language. (For locations such as the UK and US, this can be further broken down by state/providence.)
Keep in mind that geo-targeting can also be applied to not only status updates, but other post options as well: photos, links, and even video!