Getting killed by someone trying to barrel role around me. It just does not happen.
It is not that I am good. It really is not that effective a technique. I recognize it immediately and adjust. It is only a technique to use against someone playing the game less than 3 months or so.
Its effectiveness on veteran players is a myth. 
On the upside it sure is pretty.
I'll say that is mainly because it is primarily a defensive maneuver used to dodge a BnZer or to attempt to reverse the fight from a defense to offense, if the BnZer doesn't get out far away from the bullets, they might get shot from a well executed BRD. I use the Barrel Role Defense almost every sortie vs opponents that jump my 6. A lot of times I don't necessarily kill them on the first go around, but using the BRD, I can avoid the shot and have a chance at making a shot on my opponent all in one swift motion. I may not get you the first time but it causes you to have to go around another time in order to try to kill me and that can kill a lot of your E and alt.
The reason is that some players haven't perfected it enough is beacuse they don't use the vertical enough or get flaps out and cut throttle enough, or the timing is off, so its just a very difficult maneuver to do correctly and effectively.
Many don't even know what it is. It blew my mind the first time Cooley show me it.
IMO, it is one of the best defensive maneuvers in air combat and if you can get the move down correctly, you will avoid dieing a lot and also have a shot attempt on your opponent. I'd highly recommend learning this maneuver as it will save you 9 out of 10 times. It isnt so much about getting the kill as it is avoiding getting killed, but still being able to hold some E and get the enemy to over shoot, causing them to lose more E and and Alt than before, where they can now get picked or may not have the speed to climb away after the second over shoot.
It's all about execution.
Good on you for avoiding it BTW, that does take a lot of air combat understanding as well and can done using 2 sharp emmilmanns after an overshoot. Sometimes you may even be able to rope them!
