Think of it like talking on a webcam with your relatives back home, but with less talking and more shockin' out.
>but I fail to see the purpose of simultaneous listening across the world.
It's just the simple pleasure of knowing that over the other side of the world, your friend, who presumably responds to the music in the same or a similar way to you, is currently having that same response at the same time. This knowledge could reinforce the sensation of a shared experience, especially if you're recreating a shared listening experience from the past where you were physically together.
Obviously it doesn't really matter because you have no way of knowing what the other person is actually doing at that time unless you have some other out of band communication, a webcam or whatever. You would have the same sense of shared experience if spotify only told you it was syncing but actually didn't, how could you know? However, we are talking about emotional phenomena here and as such these logical stipulations don't really hit home.
EDIT: Also using it to synchronise two entire parties would be fun.
Most of the time that isn't happening, but when we want to, it'd be nice to have something to help with that.
Not that it's a huge hassle to hit 'play' on whatever youtube video he sends. The 10-20 seconds of lag aren't really that important.
You see that a friend with a similar taste in music to you listens to song you don’t know so you click to listen in. That would be useful. This integration also could allow your friends to play music for you. (“Hey, listen to this cool song I discovered!”) I find myself sharing links to songs (mostly some video on some video platform) all the time when chatting with friends, so maybe this will be an easier way to do that.
Whether or not this is actually useful depends in my opinion mostly on the UI and how easy to use it is. If it is more tedious than googling for the song and listening to it that way it won’t work.
Imagine a chat session with someone where you're listening to the same soundtrack (chosen by participant(s)). Potential for epic interactions.
Haven't you ever been in your friends car and heard a song on their CD and been like "wow that song is great, I wanna get it!" - same concept.
Music is so ineptly social.
A quick Goog brings up:
http://en.wikipedia.org/wiki/SHOUTcast http://www.serverroom.us/shoutcast
Why? Maybe this function will be an interesting experiment, but I just don't see it working out. Honestly, does anybody really care if their friend is listening to the same song (in a different geographic location) simultaneously? Where's the value added? What does anybody gain from this? Maybe social has a place in music, but this isn't it.
Edit: I'm not disputing the fact that bonding doesn't happen over music (clearly it does, as anybody who has ever listened to a song with another person would know), but I fail to see the purpose of simultaneous listening across the world.