When people decide to blast their headphones loud enough for others to hear... Not everyone shares the same tastes of music as you do, guy. >.>
My favorite moment of this was back in high school when I could not only hear, but recognize the song they were listening to over my headphones (which mind you I also use in-ears which generally have good sound isolation). It was Chop Suey by System of a Down.
There's a kid who comes in where I work with a CD player. I can clearly tell he listens to death metal.
Maybe cause their ears are too small and the earbuds can't fit in their tiny, child-size ears... *raises hand* I seriously need to go to Toys R Us and find some kiddy earbuds and see if they stick in my ear instead of barely fitting.
You know what's worse? When your neighbors blast their music so loud you can hear it down the hallway. At three in the morning. And it's not even good music.
Probably my only pet peeve. It's so annoying because I want to know what they're listening to but it's not quite loud enough to hear. I'd rather hear nothing at all than have my curiousity poked at like this.