What are they up to? They're listening to their Apple iPods and doing what journalist Steven Levy calls "escaping reality via the White Earbud Express" in The Perfect Thing, his book about the iPod.

But while the iPod has been blamed for creating a sea of zombies who don't interact with one another because they're transfixed by their personal soundtracks, the introduction of smart phones that can double as boom boxes such as the Apple iPhone, BlackBerry Bold and T-Mobile G1, is prompting more people to share their music with everyone around them.

Just ask Danny Balay. The 27-year-old Orlando, Fla., resident loves his iPhone and his music, particularly, Johnny Cash.

But the white earbuds don't fit him, and he doesn't like wearing big bulky headphones when he's walking around. So instead, he'll listen to music through his iPhone's built-in speaker while he's pushing a shopping cart at Walmart, walking around a park with his fiancee or even while eating at Subway. He doesn't blast the music, but he plays it loud enough so other people can hear it. He also makes sure to choose songs that won't offend anyone.

"I'm not going to play something vulgar, like a Lil Wayne song while I'm shopping at Walmart," Balay said. "I've never had anyone actually come up to me and ask me to turn it down. I have had people comment on the song, or ask me, 'Hey, what is the name of that song? I've always wondered what it was.'"

Balay said he considers walking around with headphones on to be a bigger social offense because they signal to those around you that you don't want to be bothered. By sharing his music, he's inviting people to interact with him. And if he picks the right song, he just might brighten someone's day.

Just like the rise of the iPod zombies, this trend is more prevalent in big cities. A friend of mine in Washington tells me that he's seen several people walking the streets with music playing from their phones in a manner that recalls the boombox craze of the 1980s and 1990s. Like those who have seen Balay out and about, my friend was intrigued and entertained, but not put off. He got a kick out of seeing how well the people playing the music matched what he viewed as their personal soundtrack.

To be clear, I'm not suggesting that people throw away their headphones and use their phones to channel John Cusack blasting Peter Gabriel in "Say Anything."

As Emanuel Pineiro of Kissimmee, Fla., can attest, there are still plenty of places where people want peace and quiet. He was recently reading a newspaper in a doctor's office waiting room when he was disturbed by a hip-hop song playing nearby. He looked up and saw a man intently staring at his iPhone. A few minutes later, the music changed, and Pineiro looked up to see that the man was playing a game.

Finally, after getting glares from other patients and nurses, the man got the message and left the room.