I'd love something like this, but I don't see any upside for iTunes or Spotify to support it. Anything that makes it easier for a customer to switch to a competitor is something they're going to resist.
They have plenty of upside to allow import through this format, as you can just upload your Winamp (yes, I'm old) playlist to Spotify and immediately migrate to their service. I'm hoping there'll be enough user demand that they'll choose not to appear evil and support export as well.
