I use Yahoo! Music for most of my music-listening at work. I like the service and at $60 for two years (they had a special when I signed up, the regular now is $72/year) it’s a great deal. [UPDATE: Corrected cost, I had remembered incorrectly.]
The system allows you to customize various stations by giving it feedback about what songs and artists you like. It’s a helpful feature, for the most part. But I think services like this might want to tweak the system so certain songs are kept off playlists at certain times of the year. I am not suggesting that they should be banned, of course, but perhaps not streamed unless sought out actively by the user.
I may like Boney M, but I really have absolutely no interest in listening to a Christmas song from them in the middle of May.
This reminds me of the dance club I used to go to in Budapest when I was in high school. One of the most popular Jive songs at the club was Rockin’ Around The Christmas Tree [audio]. It was very bizarre to listen to it over and over again in June.