tvspecv:prejudice plasma people!
He he, I happily admit that I never bought into the ambilight idea. I guess you either love it or hate it.
It is definitely a good idea to have some lighting behind the screen as it eases watching for the eyes.
But it should be homogeneous D65 light to complement the picture and perceived contrast ratio rather than influencing the picture.
Adding various different colours to light will inevitable screw up the intended picture and how you perceive the colours. As a purist I cannot accept that.
As for 3D with ambilight I am not sure we have the same situation as for 2D. I could easily imagine this would confuse the 3D experience even further, in addition to the remarkable crosstalk on LCD screen as highlighted by Max