This may be the case, although, I'd argue that Facebook really doesn't do anything that makes it any easier for you to connect with your friends and family than email does. However, let's say it does, that still doesn't mean Facebook is world changing, it just means its a better mousetrap.
And email doesn't make it any easier to connect with friends and family than paper based mail does. Oh wait.. it does...
Facebook has a number of features for communication that email doesn't have:
1) Passive communication: the fact you can go and check someone's profile and see what they have been up to is very powerful
2) Default public communication. By making communication public by default it lets your other friends and family benefit from any communication you do with a 3rd party
3) No email addresses - people change email addresses a lot more than they should. The only comparable problem on Facebook is when women get married and change their lastname, but I've never seen any problems arising from this.
That really just scratches the surface of the differences.
Sometimes, doing something better really is enough to make a huge difference.
Yes, but Facebook is fungible. In the same way that MySpace and Orkut were. The only thing that's holding people on your website is other people and a bunch of dumb games. You can say whatever you want about Google, but there is not a single search engine today that is as good in all cases. That's why I'll bet my money that 10 years from now Google will be well and going strong, whereas I have no idea what will happen to Facebook.