If anyone is interested, we have launched a new website which hosts your playlists and connects you to other users based on your music interests (from the iTunes song data). We are now looking for people to join as beta testers.
It's absolutely free and anonymous and all you have to do is upload an iTunes playlist XML file, which of course can be a smart playlist. We're looking for suggestions and comments on how to make it better.
For example: Right now you can click on an artist in your list and Musicmobs will return other users who also have songs by that artist. You could then click on that user and see what else they have. The information is sorted in a few different ways including: artist play count, song play count, and user rating (the 1-5 stars rating).
Please let me know what you think! I really appreciate any feedback.