Depending on the area I use use the left lane at times when not passing, going from Nampa to Boise there are a two freeway entrances where nobody seems to like to merge at freeway speeds, so I get in the left lane before I reach them. I have had a few times that I have had to slow down to 50 because I couldn't get over, so I attempt to before that. If however there is someone coming up behind me speeding I will move over before they reach me. In most areas if there are more than 2 lanes I drive in the middle except to pass (sometimes I have to pass in the left lane because people driving slow in the fast lane)
I would rather stay back and give people room, if a lane is open I will pass, other than that I like it when I have at least 4 or more car lengths between me and the other cars if possible, and when also when in more traffic I will sometimes stagger myself to allow sudden lane changes by other drivers, its better then them not seeing you and changing lanes when you accidentally get in the blind spot or they just don't pay attention.
And in the video the cop broke the law, illegal lane change, he didn't use his blinker to move back to the left after his lights where off.