Facebook has given a big step in simplicity with its Graph API and the creation of the Open Graph protocol, now more than ever it's easier to read and write data from and to the socalled social graph.
You could turn your webpage into a fully-featured Facebook-like page, just like if you were inside Facebook, you can give your users the ability to sign in with their Facebook credentials, customize your users' experience with parameters taken from their Facebook profiles, you could add a Like button to every object in your page as images, songs, articles, etc., tell your users which friends of theirs have liked your content, and a lot of things more, oh, I forgot to mention something, all of this with total ease. Yes, I know you could do it with Facebook Connect, but I said "with ease".