My car has what is called adaptive cruise control and it can also tell the distance between you and the driver in front of you. Adaptive cruise control is when it matches the cars speed in front of you. 120 yards is the limit. Even with 100 yards at 60-70mph, 100 yards is about a 3 second delay which is what's recommended, and not incredibly excessive.

Agree with the left lane opinion though. Unfortunately there's only a few opportunities between the three opportunities of passing where the left lane is even an option.