Jumping in late on this thread...
I hate the selfie sticks. I'll give you 2 recent examples as to why:
Splash Mountain. The couple in front of us spent the entire ride with the stick extended aiming towards them on the ride. The arm extended outside the vehicle, and then above them so they could spend the entire ride making kissy faces at their gopro while on the ride. As the person BEHIND them, not only was it distracting, but I was in the position to see it banging against set pieces that are NORMALLY out of reach.
Second reason:
People extend them with no care to those around them. I have gotten whacked in the face, hard, by someone recklessly swinging their selfie stick in the parks. As crowded as they are, I am sure this happens a lot. I can EASILY see why they are swiftly getting banned. Enforcing it will not be easy, as more often than not when someone in the parks is told to stop doing something, they only comply for as long as someone is watching them.