Facebook groups is a distinct feature from facebook lists.
Facebook lists are the same feature as Google circles. And the only reason you didn't know this already is that you did not care enough to look, so circles cannot be all that much of a killer feature.
To utilize "Facebook Circles" first you must put categorize some friends into a list.
https://www.facebook.com/friends/edit/
Click "Create a List" and drop some friends in. I have restricted permissions for anyone not in a list. A "Good People" list for those that I'll share anything with, and a few others.
Now to utilize sharing type some stuff into your status box. Anything, but lets go with "I can have circles too."
Now click the lock icon to the bottom right of the status entry widget. It will say "Make this Visible To:" And you see have a text box you can now type your list name into. I type "Goo" and it auto completes "Good People"
You can even exclude lists! So you can have a "Friends" list and a "Coworkers" list with people who overlap, but then post status that only go to your "Friends who are not coworkers."
The only difference is that google puts the UI in your face, which I like. But saying that Facebook cannot do this is absurd. It's there, you just never cared to look.