I use a lot of music web services but I don't like to invest in this sector. Nonetheless, it's an area that I spend a lot of time thinking about. I've written endlessly on this blog about the music web services I use, why I use them, and where I think the music web is going.
The most interesting music web service to me has been audioscrobbler (aka last.fm). I'm not all that interested in last.fm as a social network, but I am obsessed with it's value as a data asset. I report all my music listens to last.fm via the audioscrobbler technology and it has built a deep data asset on my musical listening habits (and therefore musical taste).
I use audioscrobbler too, but not as deeply as Fred Wilson
, one of the best tech bloggers around. If you look on the lower right-hand side of my blog layout, you'll see a chart that's tied to the last.fm API - click on the blue arrows and you can scroll through the recent faves (the ones I've listened to via iTunes and on my iPod , anyway). Warning: acres of classic rock.