Some services line Netflix have an annoying geolocation restriction that made them unavailable outside the United States. In case of Netflix, this is due to licensing issues. It's not a slim difference: do you want to be able to access just over one thousand movies, or would you prefer to have access to over thirteen thousand movies?
Have you ever tried to figure out how to make Squid authenticate users according to your own exotic rules? Users are in a DB? Are you using an ActiveDirectory? Users/passwords are authenticated by a java class? Everything is possible. Here I intend to explain how to make your own custom authentication helpers so you can develop your own routines for your own requirements.