When someone first starts training in MMA, BJJ, or submission grappling, you learn the basics first, but what everyone wants to do, is learn the exotic, entertaining, and or flashy submissions. As you progress through your training, you realize that those exotic, entertaining, and or flashy submissions aren't that easy, or even practical to pull off in competition. For that matter, they're not even easy to pull off in practice/sparring. So when one of those submissions, such as the flying arm bar gets pulled off, it's as exiting to watch as a successful trick play in football. The surprise and it's low percentage success rate give it the "wow" factor that fans in any sport can appreciate.
Check out the fight video of Carlos Valerie and Daisuke Nakamura going at it at the M-1 challenge. Not too many chingasos needed in this fight.
Here's a nice intructional video by Submissions 101 on how to do the flying arm bar.