Allow anonymous users to create nodes after Facebook or Twitter authorization

I've built sites with users registering and integrating their twitter and facebook accounts, but I'm trying to streamline the process of allowing anonymous users to create content without registering for my site. I've been through the various FB and Twitter modules, rules, etc, and I'm wondering if the following is possible.

I have a content type called "message", it uses various CCK fields to help the person fill in their message, and have it displayed consistently. Here's the workflow I would like:

1) Anonymous user fills out CCK fields, clicks "Save"
2) Anonymous user is asked to authenticate using Facebook, Twitter, or Open ID
3) After user is authenticated the "message" is posted to the site

The whole point of the user authentication is spam prevention, otherwise it would just be easy to let anonymous users create the "message" content type. The only way I can think of doing this is having users create accounts first, and that kind of defeats the purpose. The users don't need accounts, they just need to be authenticated as a human being before allowing the "message" to be posted.

Does this make sense to anyone? I've been trying loads of different ways to get this done, but just can't seem to come up with a workflow for this. Any help, advice, ideas or guidance would be very much appreciated! Thanks!