Again with the two posts in one day. It's madness, I tell you, madness!
I know I'm late to the game on this, but I've started playing around with the streaming radio service called "Pandora". It's an offshoot of the Music Genome Project, which combines the original aim of that project with a much more dynamic means of accomplishing it.
In basic terms, you start out by telling Pandora about a favorite band, song, or type of music. It will then start a streaming music station based on that. It looks at elements typical of that music, and chooses items that are both stylistically related, and and that are appreciated by others who like the same kind of music. From there, it gets more hands-on. You can proceed by simply telling it whether or not you like the songs that are playing, and it will tailor further selections that way. Along with that, you can simply continue to enter favorite groups and songs directly into the system, and it will blend in those considerations. You can do this with a single music stream, or you can separate out several different ones along any criteria you wish (mood, genre, etc.). Myself, I just cram them all into one. Most of my circle of friends are into "musical whiplash", or rapid genre shifting when it comes to music. It comes from loading an eclectic music collection into a MP3 player and hitting random. Pandora lets you do that writ large, as well as throwing in music and artists that you may never have heard of or considered before.
I'll admit, I have rapidly become addicted to the service. My favorite part is that you can ask the system why it chose a particular song, and it will give you a list of reasons, such as "...it features modern r&b stylings, funk influences, disco influences, a subtle use of vocal counterpoint, and a subtle use of vocal harmony", which happens to be playing as I write this. The new IPhone even has Pandora compatibility. I think it beats syncing a play list, hands-down. Check it out.