Rainbow Six Vegas and it's sequel are infamous for the arduous task of achieving elite status. Done by the book it takes hundreds of hours of play to top out. Some dedicated players never do. Yet some players seem to get there almost overnight. This little bug, is just one way they're doing it.
From the Video: "Using this method, you accumulate up to 2 XP per second as long as you tape down your left trigger and don't touch it."