Streaming video widgets like the one for YouTube will slow the forum down if we have a megathread containing a bazillion of them. This is not an issue with basic hyperlinks.
I created the FM/8-Track sub-forum so we could post smaller individual threads for streaming videos without worrying about them getting buried under a bunch of general discussion threads. Just figured it would make it easier to come back and replay your favorites from time to time. If you want to reply to a large video thread, you might want to only use hyperlinks in your replies.
Or you can just start a smaller parallel thread if you want to post streaming vids. Use your judgement. No one should view a parallel thread in a negative light; it's just a way to keep the forum chugging along. This applies to non-music vids as well. The streaming vids should look pretty good against the forum's black background.
If you're on a thread with multiple streaming videos and you stop one to listen to another, make sure you hit the F5 key to clear the cache (i.e. the red buffer ribbon). This should minimize buffering slowness, if any, for the next video.You also can click on the streaming video while it's playing to go directly to the YouTube site and then navigate on the forum while listening to the FM/8-track. 
As a courtesy to the original YouTube (or other) poster, I would recommend giving them credit in the post for a streaming vid. Something like "Posted by so-and-so on YouTube." Don't worry about it for the hyperlinks.
Our forum is probably visible to other forums on the hosting service and you never know when an original video poster may be watching.
I am not anticipating any performance issues from the video posts. Like I said, use your best judgement.
Thanks for reading this and Happy Posting!
-Mark
