I think Last.fm might have been a better friend finding and dating app than any of its contemporaries or anything that came after. Seems like everyone in this thread or anyone I know IRL has a story of making a good connection with someone via it. I know I'll always cherish the people I got to know on there.

Music taste is probably the all time best indicator of compatibility tbh. You can go to shows together. You can jam out in the car together.