Facebook definitely does have that. They're called Friend Lists. Click "Friends" on the left hand side, then "Manage Friends" at the top right, then "Create a list".
That said, Google+ is pretty neat. I hope it doesn't die out like Buzz did.
I'm hoping for Google's ability to design interfaces to move across, considering Facebook is still awkward for a lot of things. Chat, I'm looking at you :P
I'll give it a shot, just so I can be one of "people from the beginning". Considering I joined Facebook late, out of protest. Not that I expect it to succeed, however.
Facebook is bigger than MySpace ever was. Not to mention that it has two major factors to keep it in the top spot. The first is the support from the internet in general. You can sign into so many places with Facebook, there's Apps for almost every mobile platform, etc, etc. Also, one aspect where MySpace failed was that it was overrun with a childish stigma (I'm not refuting that, lol), so you had very few adults join. On the other hand, I'm sure that many of your parents use Facebook, whereas they would have avoided MySpace. Now I'm not saying that Google+ won't have the mature and polished reputation that Facebook has, but the key point is that older audience. The older you get, the less keen you are to adapt to change, especially when you don't see a good reason. As such, a larger chunk of Facebook's member-base will be inclined to stay put, compared to that of other social networking services.
If they really want to succeed, they're REALLY going to have to push it and make it flatten Facebook without just giving them ideas to copy. They not only need to make changing the obvious choice, but members need to have nothing to lose. This means the ability to retain friends from Facebook and really just to avoid missing out on anything.
Did anyone else notice how much it sounds like Googleplex/googolplex?