There are two styles of embed codes that are available for YouTube videos; youtube and blogger blogspot; iframe ; youtube autoshare

Compare the video window with the insert button of the blogger post editor (
http://ex-ample.blogspot.com/2011/06/best-video-format-for-blogger.html
and
http://ex-ample.blogspot.com/2011/06/dont-use-insert-video-of-blogger-editor.html)
and the video inserted with the embed code given by youtube
when you upload your video (see the HTML code of this post ).
This HTML code uses object and embed tags:

---------------- or via youtube URL; just clic on this link:
http://www.youtube.com/watch?v=H0v5tGIsne4
The ID of this video is : H0v5tGIsne4 (11 characters).
------------------
if you use the embed code given by youtube with the "share button",
the tag is "iframe":


There are many differences with the video of the beginnig of this post.
In your blogger post editor, you can see the first image of your video (iframe).

Snapshots : the "iframe code"

----------------Conclusion:
There are two styles of embed codes that are available for YouTube videos. The new embed code begins with iframe... and supports both Flash and HTML5 video and then it is the best method. The older style of embed code begins with object... and only supports Flash playback.

Ref:
http://www.google.com/support/youtube/bin/answer.py?answer=171780&expand=UseOldEmbedCode&hlrm=en-GB#oldcode

-----------------------

the link between your blogspot.com and your youtube is manual (this post) but with other web services (facebook, twitter, reader, buzz, orkut, MySpace; 6 services @ june 2011), it 's automatic:

See some snapshots of youTube autoShare :

 after linking youtube access with twitter and buzz, you will get the messages:

Then all your activities in youtube are published to twitter and buzz...