I tried streaming a 3D YouTube video today. It worked well. However, I had to stream it from my Set Top Box, because if I did it through my Bravia, I could not select 'Side-by-side' mode from the 3D menu. If I streamed from my STB, I could select the appropriate option on the Bravia.
There needs to be a facility to be able to select YouTube from the Bravia's menu, and still allow all options of the 3D menu to be accessed.