I was walking home from the convenience store today, having refreshed my supply of Twizzlers, when I walked by a girl with her iPod, singing loudly. Some people find this kind of public display annoying; I am not one of them. In my mind, it's an activity roughly analogous to the people who do inappropriate things inside their car, forgetting that people can see them. In both cases, technology provides an imaginary private space. There's some difference; a car provides a physical space as well, what with the whole metal and wheels and so forth. And the method of piercing is different; you hear the singing walker, but you see the motorist who decided to spend the time at the red light examining the content of his left nostril.
You might tell from the comparison that I'm a little more tolerant of the former act than the latter. This would be true--largely because I vastly prefer walking to driving, and I'm a fairly vocal singing perambulator myself. But there's a level of unconscious pleasure to it that I really like as well. Singing along to a song no one else can hear signals a sort of joie de vivre that I could support (and practice, when the mood hits me). I'm not saying that I'd like everyone to burst into Broadway showtunes whenever they leave the house (although with a bit of coordination, that would be awesome), but every now and then, it's nice to hear.
That said, people that blast their music over the speakers of their car are still assholes.
As a coda, when *I* walk down the street singing Avril Lavigne tunes, I receive somewhat fewer smiles and more raised eyebrows. Marshall McLuhan was right; the medium is the message.