Discovery does have streaming.

http://dsc.discovery.com/videos


There are well over 15,000 clips from various shows and several full episodes of "MythBusters", "Auction Kings" and a couple of others.


Not as many as PBS with 16 of their most popular shows having full episodes
http://video.pbs.org

or History Channel with 14
http://www.history.com/videos

Or EWTN that streams 100% of their content as well as archives it.
http://www.ewtn.com/multimedia/index.asp

Discovery will catch up. Free Online streaming is not going away.