You-tube has added hi-def (HD) viewing options for many of their videos. From the lower right of the YouTube viewer, you can select HD720 or even HD1080 for some videos.
Unfortunately, videos can sometimes stall on even the lowest definition (360p) setting. This can be annoying especially if the resolution is not important to you. I often watch videos primarily for the audio and would rather have a lower definition option where the video stream never stalls out in the middle.
You-tube is focusing on HD, but should consider adding an LD button to the videos it hosts.
Visit: Low-Tech Times / Old Dominion Wildlife YouTube Channel