Mumford and Sons is to music what going to an Indian restaurant and asking for a chicken tandori with a "1" on the hotness scale is to food. People enjoy it because it's something new, something a bit off the beaten path, but still accessible. Someone enjoying Mumford and Sons does not in any way take away from your ability to enjoy music by The Pogues or Tallest Man on Earth. If anything, it gives you the opportunity to share further with people. "Oh, you just discovered Mumford and Sons and like them? Maybe you should check out some of these guys. They might be right up your alley." Everything out there has something that is more appealing to "mainstream" people. Cars have Honda Civics. Folk music has Mumford and Sons. Coffee has Starbucks. On and on. The purists and the eclectics though? The people who have a true passion for their hobby? They still know how to find what they want.