I think they do serve some *slight* purpose in that the waving of the flags does seem to make people proceed through the intersection at a faster pace. The problem, of course, is that they don't have any clue as to how to wave those flags in a manner that makes their intent clear. I've also had them let me go through a "no turn of red" intersection when there was no traffic to otherwise stop me. What burns me is when they also take control of the traffic light signal box and manually decide how to run the lights - this is when things really truly get messed up.