I remember when all my YouTube videos were encoded 4 frames out of sync. Times sure have changed. The YouTube video player is now widescreen, which is great because it really lets you get the full resolution of your widescreen videos, but it’s not so kind to older videos that haven’t been encoded in “high quality”, like the copy of Two Night Stand I uploaded in 2006. Embed codes still default to 4:3, but you can customize the size to whatever you want. Unfortunately the thumbnail seems to be letterboxed, so in a 16:9 player it ends up window-boxed.
Update Dec 6: Things have changed even more. Embed codes are now widescreen, and thumbnails are no longer windowboxed. Even better: 720p!!!!! If you’ve uploaded a 720p or higher video, add &ap=%2526fmt%3D22 to the end of the param value and embed src urls in the embed code and you can actually embed 720p YouTube videos on your website. To view 720p videos on YouTube, add &fmt=22 to the end of the url.