Confirming the same problem under Linux 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt20-1+deb8u3 (2016-01-17) x86_64 GNU/Linux:
$ livestreamer http://www.ustream.tv/embed/9408562?v=3&wmode=direct best [1] 3670 bash: best: command not found $ [cli][info] Found matching plugin ustreamtv for URL http://www.ustream.tv/embed/9408562?v=3 [plugin.ustreamtv][warning] python-librtmp is not installed, but is needed to access the desktop streams Available streams: mobile_284p (worst, best)