I've spent a fair amount of time making a number of playlists across various genres. Every so often, original tracks are no longer available on Pandora, and the program substitutes a different version. Usually the substitution is some awful re-recording or remix.
Instead of auto-substituting songs no longer available, just gray the track out. I don't know if it's to give the illusion they're not losing catalog or some other reason, but in the end, I invariably remove the substitute. It's a literal playlist destroyer.
My spouse is an employee, so my service is free. If I paid for my sub, I would have switched services a long time ago for this reason alone.
Moderator Edit: Changing title for clarity
