Hopefully, I can get you the answers your looking for below..
I mean: for every user registration in every website of every country it is necessary that he agrees with the terms of service and privacies, unless you want to be outlaw.
There's no requirement that there be a checkbox that's displayed during the registration process in order to do so. There are many, many ways to ensure your users are aware of and agree with the terms of service, even while using the Auto registration feature of JFBConnect.
1) You can use the "New User Redirection" feature of JFBConnect to direct all users who just registered to a nice welcome page, explaining your site, benefits, and, of course, that using the site is bound by the terms of service and privacy policy.
2) You can put a note at the bottom of your pages saying "By use of this site, you understand and agree to our privacy and terms of service". That works for guest users as well, which is a bonus.
3) You can add just that note to a specific "Login/Register" page where all users are directed when they need to login.
Additionally, for Facebook at least, when a user "Approves" your application in the popup, there is a link to your privacy policy (when set in Autotune). By approving your app, they've already agreed to your terms.
If, as suggested, I use the normal flow with JFBConnect as registration component, the only advantage I have is to have some fields already filled-in, and however the user as to choose the password, etc., so a very similar process as if no facebook connection was used....
Regardless of the flow you use, there are other benefits to having a user logged in with their social network credentials:
1) Facebook Open Graph Actions can be posted on their behalf automatically.. this pushes activity they take on your site to their timeline, which is great for promotion.
2) Autotumatically logging returning users back in when they're logged into the social networks
3) No need to remember a new set of credentials just for your site
4) Less registration fuss with either less fields, more fields pre-filled, or no fields at all.
Just so you know, Amazon, Facebook and most other major sites do *not* have a checkbox a user has to click. They all use a "By using this site, you agree to our terms" line of text. If your users don't like it, they should be able to contact you to delete their account.
I hope that helps explain, but if you need more assistance, just let me know!
Alex