I have a new blog and I was looking for something like this. The "bbc max-length" topic reminded me about this idea.
http://lab.leocardz.com/facebook-link-preview-php--jquery/
Maybe implement it as pure JS to avoid the server having to do it? More than likely a plugin, but I think it would be cool for at least when you add a link via the menu.
Interesting... is there anything I don't find interesting? xD
Would that excerpt of the link be posted into the message body?
Or into a separated entity?
I would do it with a new BBC tag
I can see more awesomzz things coming in :P