Adding inactivity to injury, this is especially true in locations where many people exercise accompanied to music, airplanes (hey, it's hard to return those seats to their upright positions), the New York City subway system, and the streets of cities other than Mountain View, CA. Indeed, most WiFi-friendly environments are also laptop-friendly and thus support access to not only Yahoo Music and its competitors, but high-quality free internet radio from last.fm, Slacker, and others.

ENGADGET: Switched On: Music in the air (Part 2)