Problem: you can't remove someone from your playlist when it fucks everything up.
Some months ago I thought it'd be nice to add John Jarvis to my Bluetech channel. Boy, was that a mistake! Pandora took this to mean I wanted to hear every piano soloist in the universe.
Now it's not uncommon for me to go to Pandora and then expend--right away!--my three dislikes per hour clicking away piano soloists, three in a row, even though I've now done this just about every time I've tuned in. It's like the algorithm isn't getting the hint that I don't want piano soloists in this channel except for John Jarvis.
...and in fact I don't even want John Jarvis any longer, because it plays about three tracks of his, and that's it. But while you can "add variety", you cannot remove variety when you realize that it's made a hash of your playlist.
So not only does it keep trying piano soloists, but it tries multiple tracks from the same album, so even if I tell it "never play X by So-and-so" it's likely to pop up another track by So-and-so a few songs later, and after I've told it never to play X, Y, Z, AA, or AB by So-and-so, it still pops up AC by So-and-so.
Three songs by the guy I specifically added. Five songs from the guy I tell it never to play every time it tries. WTF.
Meanwhile, the seeming hundreds of songs that I've liked in the channel are ignored, so when I click my three "fuck no" selections it then usually pops up something random that I don't like. "You said you didn't want to listen to piano, so here's a song with flute and doumbek! You like that, right?"
On balance Pandora is pretty worthwhile, but that doesn't mean it couldn't be better.
The good thing is, I know exactly what I have to do to get a channel of piano soloists: make a John Jarvis channel. Of course, knowing how this kind of crap works, I bet if I made a channel specifically to listen to piano I'd get nothing on it but acid crunk and ambient dub. Argh etc.