IP delivery
In this video by Maile Ohye, a Google senior support engineer, we can see strategies for serving different content based on users location, or, more precisely, on users IP address. The strategy used by google.com is shown as well as advices and some HowNotTo use.
The most important point discussed is that you must not use the same url to provide different content. A url must have the same content regardless of who is visiting it.
See the complete video below, it's totally worth it.
http://www.youtube.com/watch?v=XWfqyy7J34s
