A rather large portion of my CD collection was encoded using the Ogg Vorbis codec, some even used the beta codec. The QuickTime architecture seems to be transparent to codecs as long as the appropriate decoder file is available. This means iTunes plays ogg files without even carrying about the file type, as it merely passes the decoding to QuickTime. However I have not been able to figure out how to use QTSS to stream ogg files yet - technically the fact the mdia is ogg should not matter.
Has anyone else had success providing ogg streams?