The worst race I've ever seen for this is the Army 10 miler.  They go through this huge effort to color code your bibs based on your estimated finish time.  The start corrals are color matched to bibs with big balloon arches.  The corrals are at least 50m long if not longer - it took several minutes to walk from the back corral to the start corral.  They have uniformed army personnel standing at each corral. Despite this, the race did not enforce the corral colors AT ALL.  People with corral 6 were crowding corral 1.  Adding insult to injury is that the race lets army personnel start ~10 minutes before the rest of the field.  In addition to weaving between all the corral-violating fats, a couple of minutes into the first mile we run into practically entire companies of fat women in fatigues walking 6 or 7 abreast.  I lost at least 30 seconds in my first mile weaving between these assholes. The race also costs $70.  For a 10 miler. Why do it you ask?  Great crowd support and the course is pancake flat.  Once you get past the fats it's a very fast course and great for PRing.