PBS Geolocation
Ron Deibert discovered that PBS.org is restricting access to some of their programs by geolocation filtering.
Generally, geographically-targeted filtering uses geolocation technology to determine an Internet user's geographic origin by looking up the requesting users' numerical Internet protocol (IP) address in databases that associate IP addresses with particular countries.
When users access the programs from locations other than th USA, in this case Canada, an error pop-up occurs:
We're sorry, due to rights restrictions this program is only available for online viewing in the United States, its territories, possessions, and commonwealths. You appear to be connected to the Internet from outside these areas.