That is a great question. It's like when you go into a store do you like the ambiance music? Me personally when I browse the internet I do it with my speakers off. Unless I wanna watch a movie on youtube or something I'm a silent browser. I wonder if there are also any "research" on sites that play music and what the stats are.
I think that music has been misused at times, like a few years ago when some sites had pretty cheesy sounding MIDI files playing when you went to a site.
I think that the site for the new movie Hairspray uses "automatic" music very effectively. I guess that's no surprise, considering that it's a musical.