You may have already noticed, but YouTube is now displaying all its videos in 16×9 format.
4×3 material is now displayed as pillar-boxed, and 16×9 material which was formerly displayed as letter-boxed is now both letter-boxed and pillar-boxed.
Thanks to Steve Martin for calling this to my attention.
(By the way, if you know the new image dimensions for submitting videos to YouTube, please let me know and I’ll share them here.)