Matt,
With the JomSocial activity plugin, you need to make sure you add the publish_stream permission request when a user logs in. More information on how to do this is at the bottom of the JS integration guide below:
www.sourcecoast.com/jfbconnect/docs/thir...ration-for-jomsocial
If that doesn't do it for you, let me know.
As for letting a user choose to post or not, right now, there's no option for that. We had another user ask about that just today (never had the request before). The post is below if you'd like to give your feedback there, we'd love to have it. It's something we'll look into, but not sure how possible it will be to do:
www.sourcecoast.com/forums/4867?p=1#p25116
Our plugin will *only* post the status to FB if the user has marked the post as 'public' in JomSocial. On most sites, if they have marked it as public, that means it will go in Google searches and be visible to anyone anyways.. though it is admittedly different on Facebook vs being available from a Google search.
Hope that explains and helps,
Alex