Since version 1.3 changed the function and form of the excerpt of the posts.
If you do not specify any parameters, the excerpt of the post created automatically with erasing formatting. If you want to keep the text formatting for the excerpt of the post then you need to use the tag
where the excerpt ends.
If you use post formats to publish media (video, audio), you can insert a short code WordPress embedded video/audio in the main editor or you can paste the iframe code into the Excerpt.
The result you can see here.