Actually YouTube has had stereo ever sense I signed up and it's pretty
decent.

If you pop over to my channel you can hear it as I only record in
stereo. In most of my latest videos I've reminded people to look in
the more info spot see the link foth YouTube HD version of my same
content... Click it and poof a new window opens the content loads a
little slower... Pause it let it load to around half way and press
play...

If you're like me with a sub woofer and better speakers than the
average I think you like what you hear. :)

But for the normal res video stereo would slow low connection speeds
down I think. I'm not sure about it though.