Noticed on the NYC subway this morning:
Seems implausible that somebody sufficiently object-cultured to own an iPod would be sloppy enough to use it with a—gasp—knot in their headphone cord. Nuh-uh. I predict that this is the start of a new urban non-verbal communication language, perhaps not unlike gang colors or those infamous backpocket handkerchiefs. But for this crew, I'm betting it's something more akin to "I've got a bluetooth-enabled phone in my pocket...sniff me," or "I've got more than 5,000 pictures in my Flickr album". (Three knots on the left plus one knot on the left means this, two knots on each means that, etc.)
Hmm, now that I'm thinking more on it, it's probably just "I'm not wearing any underwear." Yup, that's the likeliest.