is it possible?

Yes, you can do that. With JFBConnect, you can disable the "Register for this site" and Joomla login form altogether. Then, you can configure JFBConnect to create "Facebook users only", which is how SourceCoast.com (this site) is configured to where the registration is silent and a username is auto-generated for the visitor., just like your account is right now. This type of user has no way to log in with Joomla credentials, only Facebook, but every component and Joomla itself treats it like a normal user. Hope that helps explain.

We like having "Joomla" accounts too, but have heard from quite a few JFBConnect users that only allow Facebook users on their site.

As for the API, yes, version 3.0 of JFBConnect uses the updated Graph API and should be compatible with jReviews. We haven't tested jReviews specifically yet, but have tested some other 3rd party components with Facebook Connect features. Right now, 3.0 is a Release Candidate, but it's live on this site and our demo site already.. so we consider it pretty stable.

Hope this helps!

No problem. Support is what we do best. Glad to see you're a subscriber now. Thanks!

From the "Connect with their Facebook logins" aspect, that's pretty much 99% of what JFBConnect does. Can you explain "control who is able to log in" more?

We currently don't have a way to manually create a connection (we call it a user-mapping) between a Facebook user and a Joomla user. However, adding a "New" button to the usermap admin page would be trivial. Basically, it would be pretty easy to set your Joomla site up like:
* Turn off user registration
* For each user you want to be able to log in, create them a Joomla account
* Create a new usermap field in the JFBConnect administration area where you input their Joomla ID and Facebook User ID (You'd need to get this from them).

Another alternative that we're working on that may work for you is an automatic mapping of a Facebook user to a Joomla user. In this case, if a Facebook user logs into your site for the first time, IF their Facebook address is the same as a Joomla account already on your site, we'll create the connection between the 2 automatically. Currently, we throw an error because it looks as though someone's trying to register with the same email address as another user. By using this method, your client could create an account for your users and then disable user registration. If he never distributes their passwords to the users, but instead tells them to log in via Facebook, this will automatically connect their accounts and prevent them from logging in from Joomla... you'd need to hide the Joomla user details screen and other things to prevent them from updating their password, so this isn't a 100% solution, but close to what I think you're looking for.

The above request for automatic mapping is from a request from a current subscriber. We prioritize all subscriber requests, so if you choose to do so, you know you'll have the help you need to get up and running!

Both are actually new features. All upgrades are available to subscribers while their subscription is active.

The automatic mapping to a Joomla user account based on FB email is pending release either in the next Release Candidate build or the stable release (so a few days to a week timeframe)

The manual mapping, where the admin would have to put in the user's Facebook ID would be a GUI interface like adding an article (only with 2 fields: Joomla User ID and Facebook User ID). This is the first time we've though of adding this, but it would be an easy change. If you require it, we could likely make it into one of the same upcoming releases.