According to Matt, if I post the shortened link to Twitter, the text of the post will show up there. Let's see.
Twitter thinks there's some "media" there, but it doesn't display it correctly (it does open up a space for it).
Update: After a more careful read, there's documentation here for their support for oEmbed. There's also information about a few other services. What about the other 18 billion websites? How do we find out about their oEmbed support?
Here's the request for the frontiernews.org post mentioned at the top of this piece.