Facebook posting based on article access level

Yes, an option would be a good idea... but no, we don't have that setting. I've added it as an enhancement request to our issue tracker.

In the meantime, the code can be found in the Open Graph plugin for Joomla content - /plugins/opengraph/content/content.php at line 390. The existing code checks if the access variable is 3 for special or 6 for super user
Since you want to only post for Public access, you can do the following instead.
-Melissa

Thanks for the explanation. Your use case is spot on and one we've thought of before. Many sites use auto-posting as a 'hook' to get people in, so the current method hasn't caused any complaints. With how it is now, an autopost happens and that may make people register on your site. The content wouldn't fully be in the post.

One thing possibly not mentioned is that you can select which categories an autopost can happen from. If you segregate your content by category and certain categories are for Registered users only, that could work. The setting is a better catch-all, but calling that out in case you weren't aware of the category-level ability.

We'll be looking into adding this as an option in the next release. We completely understand if you want to keep some stuff private though

Thanks,
Alex

Objects are hierarchical. So, if you have a category structure of:
* Registered Category
** Reg stuff
** Reg widgets
** Reg garbage
* Public Category
** Pub stuff
** Pub widgets

You could create an object for "Registered Category" and it would work all of the Reg* categories underneath. You should even be able to create an object for "Reg garbage" itself, in which case that object would only apply to that category (in case you don't want to post from just one sub-category)

So, you can get pretty fined tuned on things.. but that shouldn't be necessary for what you're trying, frankly. We like the idea of a Public | Public + Registered setting, so that's going in in an upcoming release either way. I just wanted to point out other flexibility you may be interested in.

Thanks,
Alex