MP3 Players and other technology

I have recently been taking the MP3 player with me on my walk to work. I had forgotten about it for months, but just this week remembered that we DO have it and it is not being used at all. I love listening to music while I walk to and from work. The only hitch is that its all music I like, so I want to hum and sing along with it. I have no idea how people walk around listening to music of their choice without singing, dancing, or showing any emotion. I try, but then a song I REALLY like will start, and there I am smiling like an idiot and tapping my hands against my purse starting to hum along to the music. (I think I have caught myself before people hear...)
I think anyone with an MP3 player should walk around like the people in the I-Pod commercials. I think the world would be a much more interesting and fun loving place. Unless of course their music of choice mad them angry and want to beat people...
Maybe that's what the crazy looking guy I see every day is doing though... not talking maniacally to himself, but singing along to music... maybe...
On the subject of people appearing to be talking to themselves... I have no idea if its because we live in a big city, or just the recent craze, but many a person has the headset adaptor for the hands-free mobile phoning. I know we use them in the States for driving and talking at the same time as it frees up the hands. That makes sense. But its really odd to be walking down the street and see a single person talking to themselves. You really have to look to see if there is the hands-free set up, or they really are just crazy.