What does Facebook remind me of…?

I was thinking about Facebook today, and how it relates to the rest of the internet. It's got all the elements of the internet, but with some training wheels to make it easier.

Email? They've got their own internal messaging system.
IMs? Check. Want to make a web page? Just fill out your profile.
News, weather, sports, games - they're all there in handy "Facebook Apps." You can stay in touch with old friends, hear about your favorite topics, and get ads about things that are of interest to you - all without ever going outside the walls to the rest of the Web.

Now who else has done that before? Oh, yeah… America Online! I wonder how long before Facebook starts its own complete service, and we get the 21st century equivalent of these: