You can always check for the button text, and looking at the source code of this very page I see a few names assigned - isn't that enough for your purpose?
What is your purpose, by the way?
Comment on Re: Attaching to Particular Form Submissions
The motivator was to get a mini-feed entry on facebook when I post a new node on perlmonks. It's not horribly useful or substantial, but it's a step up from facebook's usual pokes and virtual drinks and werewolf bites.
My wordpress blog has a plugin (wordbook) that posts to facebook automatically when I write a blog entry, so I hope to copy from the plugin and translate it javascript.
The big picture is that the web is full of disparate communities, and I want to create some links.