Comment 8 for bug 451125

Some more investigation: it seems that the icy-metadata header is not the culprit. It is issued when the "iradio-mode" property of the souphttpsrc element is set to true. Getting the same stream with and without this property using gst-launch works in both cases. It also looks like doing a request on the relative path of the resource rather than the full URI doesn't affect the result, nor do the presence of the transferMode.dlna.org and User-Agent headers.
Here is the dump of the TCP stream for the following pipeline in gst-launch:

    souphttpsrc location=http://stream29.grooveshark.com/stream.php?streamKey=0d2a34d8bd9611de9770 ! filesink location=/home/osomon/temp/boudiou.mp3

    GET /stream.php?streamKey=0d2a34d8bd9611de9770 HTTP/1.1
    Host: stream29.grooveshark.com
    Connection: close
    transferMode.dlna.org: Streaming
    User-Agent: GStreamer souphttpsrc libsoup/2.26.0

    HTTP/1.1 200 OK
    X-Powered-By: PHP/5.1.6
    Cache-Control: no-cache, no-store, must-revalidate
    Pragma: no-cache
    Expires: Sat, 26 Jul 1997 05:00:00 GMT
    Content-Type: audio/mpeg
    ETag: "69546903"
    Accept-Ranges: bytes
    Last-Modified: Tue, 13 Oct 2009 02:36:13 GMT
    Content-Length: 4618663
    Connection: close
    Date: Tue, 20 Oct 2009 16:33:09 GMT
    Server: lighttpd/1.5.0