I tried to play a "custom radio station" in Amarok via last.fm today, and I get a message stating "This item is not available for streaming". I did some googling and read that this is a problem that may have been fixed as of Amarok 1.4.6. I upgraded Amarok via Ubuntu's backports and it still doesn't work. So I apt-get installed the lastfm Ubuntu package and tried that, and it still doesn't work. Depressing.
Then I read that last.fm streaming was gimped up a few months ago due to pressure from record companies. Those J-pop songs that I almost certainly can't buy in America were really bringing the industry to its knees. Thank God that was put to a stop, before all music on the planet ceased to exist.
The very latest version of the last.fm client (downloaded from last.fm manually) does let me play a custom radio, but only searching based on one artist at at time. The sucky Flash-based web player also works in the same way. Amarok does not, and I don't know what's going on there.
Neither of the official clients supports pausing the music either though, again because the music industry forbids it. I believe this is because every time someone pauses music coming from a radio station, a 20-dollar bill somewhere in America bursts into flames.
So there you have it. I'm not really going to use last.fm any more. Not a lot of point in it.