As mentioned several times, it's due to exposure. Their products are everywhere, and mostly affordable. While it's not saying much, they are actually an "upgrade" to the Apple earphones that come with iPods and iPhones. It has boomy bass which goes well with the hip-hop loving crowd.
I actually owned a pair of the "Full Metal Jacket" iem's (before learning about head-fi) - I wasn't looking for gobs of bass or some trendy styling, I actually bought it due to the life-time warranty and the notion that metal=durable. After the 3rd set wearing down in 3 weeks, I started researching and stumbled across head-fi.
Don't hate too much on its styling, as fashion is subjective (obvious statement is obvious!). I am 27, and while I prefer subtle styling, I didn't mind the skullcandy products' design.
Oh and LOL, my snowboarding helmet (Smith Variant Brim) has the "built-in" Skull Candy speakers. It's just as bad as listening to Apple earphones, but at least I don't have to deal with it falling off. Before the next winter season kicks in, I'll most likely open it up and replace the drivers.










)