If the music is played at a reasonable volume I don't have a big issue with it, I just don't get it; I can't identify the need to have music going all the time.
Not sure why the world around you isn't stimulation enough when you're on a bike. I wonder the same thing when I see guys skiing / snowboarding with music on a beautiful day. Why isn't what you're doing in the place you're doing it enough?
No music for me when I run or bike, but I do listen to music when I swim laps, though, so what do I know
To each their now, as long as we can agree that guys on Harleys with their stereo's blasting are DB's.