Code:
$ rtmpdump -r "rtmp://ustream.fc.llnwd.net:1935/ustream/test/" -a "ustream/test/" -y "ustream@llnw_1_522259_live_1" -W "http://cdn1.ustream.tv/swf/4/viewer.rsl.568.swf" -o ustream@llnw_1_522259_live_1.flv --live
RTMPDump v2.2e
(c) 2010 Andrej Stepanchuk, Howard Chu, The Flvstreamer Team; license: GPL
Connecting ...
INFO: Connected...
Starting Live Stream
581.788 kB / 4.18 sec
Caught signal: 13, cleaning up, just a second...
ERROR: WriteN, RTMP send error 32 (46 bytes)
ERROR: RTMP_ReadPacket, failed to read RTMP packet body. len: 12365
581.788 kB / 4.18 sec
Download may be incomplete (downloaded about 0.00%), try resuming
$ rtmpdump -r "rtmp://ustream.fc.llnwd.net:1935/ustream/test/" -a "ustream/test/" -y "ustream@llnw_1_522259_live_1" -W "http://cdn1.ustream.tv/swf/4/viewer.rsl.568.swf" -o ustream@llnw_1_522259_live_1.flv --live
RTMPDump v2.2e
(c) 2010 Andrej Stepanchuk, Howard Chu, The Flvstreamer Team; license: GPL
Connecting ...
INFO: Connected...
Starting Live Stream
984.074 kB / 8.92 sec
ERROR: RTMP_ReadPacket, failed to read RTMP packet header
984.074 kB / 8.92 sec
Download complete
$
It is not stable :-/