Facebook connect allows you to control what a user posts on their page about your site or product after they use the connect feature. You have the option to allow users to "Like" if they have not done so already or require a share immediately.
Facebook Connect Benefits:
-Collect valuable data on your fans (Email, Name, Friends that have also liked...)
-Track social leads back to the individual user
-Require users to "Share" to receive your offer
-Present unique experience when current fans visit your site
Restrictions of using JUST the Like Feature:
-Since it's a simple Like function, no customer data is collected.
-If a customer is already a fan (has liked before), they must unlike and then relike to receive the offer. This can confuse a user and one reason we recommend Facebook Connect for brands with larger fan bases.
Check out these two videos to give you a little more insight!