I have a playlist with a few of my band members in and i thought it would be a good idea if spotify added a button that you could press on each song that let the other people, who are in on the playlist, know that you like it.
It would be great for bands as songs that everyone likes can be used and you don't have to get together to ask who likes what, you can see it.
Just a little something that lets you know what your playlist pals think of the song.
Let me know that you think.
As @Amarro said, there's a similar suugestion here: