When an iPhone/iPad/iPod tries to play a YouTube or Google Video through the embedded player or Safari, the video does not load when going through a Proxy SG.
This is a known issue with the way the application tries to request the video by requesting byte-ranges. The workaround is to disable caching for requests that contain the HTTP header for "Range". This will have a minimal impact to performance since it only applies to the iPod-like devices, in addition to the fact that YouTube videos are served as non-cacheable so the SG would not cache them normally.
Add the following policy entries to the Local policy on the ProxySG.
define condition YouTubeRangeRequests url.domain="youtube.com" url.domain="googlevideo.com" end condition YouTubeRangeRequests