Allan,
Sorry for the delays. I'm researching this, so it's not something I have immediate answers for. I like the idea though.. but please be patient if responses take a day or 3..
I just looked at one of the links posted in my Timeline for a Like. It looks like:
www.sourcecoast.com/blog/extensions/jfbc...n_id=288381481237582
You can do the same with a link in your Timeline.. just right-click and hit "Copy URL" or something similar in your browser.
The parameter to look at is the fb_action_ids, which is 3793109186866 If you post that in the Facebook Debug Tool, and the action is public on behalf of the user that posted it (as mine was), you'll see something like:
developers.facebook.com/tools/debug/og/action?q=3793109186866
So, that does have my FB User ID, which could be used by JFBConnect to lookup if that user also has an account on your site. Figuring out the code to do so will take a little more work, but it seems feasible. The things I'd test is if all the actions (comments, Like, any custom open graph actions you have) also have the fb_actions_id. I think they will, but I don't have time to test that right now.. it'd be a good experiment for you.
Let us know if the above sounds intriguing and along the lines of what you were thinking. If so, we'll keep pursuing it. If you're planning on coding your self, that would be much faster and we can give tips where necessary. I'm not sure when we'd have time to do a full solution, but again, I do like the idea of a referral system.. just need to figure out the best way to do the integration, with what extensions, and when we'd be able to release something like that.
Feedback welcome, as always,
Alex